How do I fix or troubleshoot DynamicLinks implementation with custom domain on iOS

Question

What works

I’ve implemented Dynamic links on iOS with a Firebase page.link domain. This works fine, and I can click a DynamicLink, which redirects the user to the appStore. Upon installation and opening of the app, the link is retrieved as expected in the app.

When I change the implementation to use a custom domain ‘links.{myBrand}.com’. The dynamic link is retrieved and works as expected, when the app is already installed.

What doesn't work

When I change the implementation to use a custom domain ‘links.{myBrand}.com’, I don’t retrieve the link upon installation and opening of the app, and I can’t figure out what is wrong.

Notes on my configuration

I have this in the plist file

<key>FirebaseDynamicLinksCustomDomains</key>
<array>
   <string>https://links.{myBrand}.com</string>
</array>

Besides the aasa file on links.{myBrand}.com subdomain, I’m not using firebase Hosting

I have <string>applinks:links.{myBrand}.com</string> in the .entitlements file

Firebase debug output

---- Firebase Dynamic Links diagnostic output start ----
Firebase Dynamic Links framework version 8.11.0
System information: OS iOS, OS version 15.3, model iPhone
Current date 2022-04-20 14:48:23 +0000
Device locale en-DK (raw en_DK), timezone Europe/Copenhagen
  Specified custom URL scheme is {bundle_ID} and Info.plist contains such scheme in CFBundleURLTypes key.
  AppID Prefix: {AppId_Prefix}, Team ID: {AppId_Prefix}, AppId Prefix equal to Team ID: YES
performDiagnostic completed successfully! No errors found.

---- Firebase Dynamic Links diagnostic output end ----

Firebase consoles preview/debug Link ( ?d=1 )

Doesn't show any problems

My questions

• What can cause the dynamic link to not work with custom domains ?
• Do you have a checklist when troubleshooting a Dynamic links implementation ?