How does it come that a form submit in HTML only doesn't work in Firefox?

Question

My form perfectly submits in Chrome and Safari, but I am unable to click the submit button in Firefox. I can't find any good solution on the internet since most of them use JavaScript. I used simple html.

(input element is almost at the bottom, and the page bevestiging.html I am referring to in the form header exists in my project)

<form action="bevestiging.html" method="get" autocomplete="on" name="submit">
        <fieldset class="panel gegevens">
            <legend>Persoonlijke gegevens</legend>

            <section class="panel aanspreektitel">
                <h2 class="hiddenTitle">Aanspreektitel</h2>
                <p class="panel titel">Aanspreektitel:</p>

                <section class="panel radio3">
                    <h3 class="hiddenTitle">aanspreektitelRadioMeneer</h3>
                    <input class="panel meneerInput" type="radio" id="meneer"
                           name="aanspreektitel" value="Meneer">
                    <label class="panel meneerLabel" for="meneer">Meneer</label>
                </section>

                <section class="panel radio2">
                    <h3 class="hiddenTitle">aanspreektitelRadioMevrouw</h3>
                    <input class="panel mevrouwInput" type="radio" id="mevrouw"
                           name="aanspreektitel" value="Mevrouw">
                    <label class="panel mevrouwLabel" for="mevrouw">Mevrouw</label>
                </section>

                <section class="radio1">
                    <h3 class="hiddenTitle">aanspreektitelRadioX</h3>
                    <input class="panel xInput" type="radio" id="X"
                           name="aanspreektitel" value="X">
                    <label class="panel xLabel" for="X">X</label>
                </section>

            </section>

            <section class="panel naam inputLayout">
                <h2 class="hiddenTitle">Naam</h2>
                <label for="naam" class="panel naamLabel label">Naam*:</label>
                <input class="panel naamInput inputDeel" type="text" id="naam" name="naam" maxlength="30" size="55"
                       placeholder="bv. Jan Janssens" required>
            </section>

            <section class="panel tel inputLayout">
                <h2 class="hiddenTitle">Telefoonnummer</h2>
                <label class="panel telLabel label" for="telefoonnummer">Telefoonnummer:</label>
                <input class="panel telInput inputDeel" type="tel" id="telefoonnummer" name="telefoonnummer"
                       pattern="^0?[1-9][0-9]{7,8}$"
                       placeholder="bv. 0454326170" maxlength="10" size="55">
            </section>

            <section class=" panel mail inputLayout">
                <h2 class="hiddenTitle">mail</h2>
                <label class="panel mailLabel label" for="email">E-mail*:</label>
                <input class="panel mailInput inputDeel" type="email" id="email" name="email"
                       placeholder="bv. [email protected]"
                       maxlength="50"
                       size="55" required>
            </section>

            <section class="panel leveradres inputLayout">
                <h2 class="hiddenTitle">Leveradres</h2>
                <label class="panel leveradresLabel label" for="leveradres">Leveradres*:</label>
                <input class="panel leveradresInput inputDeel" type="text" id="leveradres" name="leveradres"
                       placeholder="bv. Herentalsebaan 15, 2100 Deurne"
                       maxlength="50" size="55" required>
            </section>

            <section class="naam geboortedatum inputLayout">
                <h2 class="hiddenTitle">Geboortedatum</h2>
                <label class="panel geboortedatumLabel label" for="geboortedag">Geboortedag:</label>
                <input class="panel geboortedatumInput inputDeel" type="date" id="geboortedag" name="geboortedag">
            </section>

        </fieldset>

        <fieldset class="panel personalisering">
            <legend>Personalisering</legend>

            <section class="panel soort radio">
                <h2 class="hiddenTitle">Soort</h2>
                <p class="panel titel">Soort halsband*:</p>

                <section class="panel radio1">
                    <h3 class="hiddenTitle">Soort halsband: dagelijkse halsband</h3>
                    <input class="panel dagHInput" type="radio" id="dagelijkse_halsband" name="soort_halsband" required>
                    <label class="panel dagHLabel" for="dagelijkse_halsband">Dagelijkse halsband</label>
                </section>

                <section class="panel radio2">
                    <h3 class="hiddenTitle">Soort halsband: harnas</h3>
                    <input class="panel harnasInput" type="radio" id="harnas" name="soort_halsband" required>
                    <label class="panel harnasLabel" for="harnas">Harnas</label>
                </section>

                <section class="panel radio3">
                    <h3 class="hiddenTitle">Soort halsband: zacht begeleidende hoofdband</h3>
                    <input class="panel begInput" type="radio" id="zacht_begeleidende_hoofdband" name="soort_halsband"
                           required>
                    <label class="panel begLabel" for="zacht_begeleidende_hoofdband">Zacht begeleidende
                        hoofdband</label>
                </section>

            </section>


            <section class="panel maatEcht inputLayout">
                <h2 class="hiddenTitle">Maat</h2>
                <label class="panel maatLabel label">Maat*:
                    <select class="panel maatInput inputDeel" name="maat" required>
                        <option value="">&nbsp;</option>
                        <option value="XS">extra small</option>
                        <option value="S">small</option>
                        <option value="M">medium</option>
                        <option value="L">large</option>
                        <option value="XL">extra large</option>
                    </select>
                </label>
            </section>

            <section class="panel kleur inputLayout">
                <h2 class="hiddenTitle">Kleur</h2>
                <label class="panel kleurLabel label" for="kleur">Kleur:</label>
                <input class="panel kleurInput" type="color" id="kleur" name="kleur">
            </section>

            <section class="panel materiaal radio">
                <h2 class="hiddenTitle">Materiaal</h2>
                <p class="panel titel">Materiaal*:</p>

                <section class="panel radio1">
                    <h3 class="hiddenTitle">Materiaal: nylon</h3>
                    <input class="panel materiaalNylonInput" type="radio" id="nylon" name="materiaal" required>
                    <label class="panel materiaalNylonLabel" for="nylon">Nylon</label>
                </section>

                <section class="panel radio2">
                    <h3 class="hiddenTitle">Materiaal: leer</h3>
                    <input class="panel materiaalLeerInput" type="radio" id="leer" name="materiaal" required>
                    <label class="panel materiaalLeerLabel" for="leer">Leer</label>
                </section>

                <section class="panel radio3">
                    <h3 class="hiddenTitle">Materiaal: macram&eacute;</h3>
                    <input class="panel materiaalMacrameInput" type="radio" id="macrame" name="materiaal" required>
                    <label class="panel materiaalMacrameLabel" for="macrame">Macram&eacute;</label>
                </section>
            </section>

            <section class="panel extraInfo">
                <h2 class="hiddenTitle">Extra Info</h2>

                <label class="panel extraInfoLabel label" for="extra_info">Extra info:</label>
                <textarea class="panel extraInfoInput inputDeel" id="extra_info" name="extra_info"></textarea>

            </section>


        </fieldset>

        <section class="panel verstuurKnop">
            <h2 class="hiddenTitle">Verstuurknop</h2>
            <input type="submit" value="Verstuur">
        </section>

    </form>