One of my iframe is not working/loading ios ionic

Question

One of my iframe is not working/loading in IOS only (mobile and emulator) while it is working fine android/chrome/safari. It happens to only one iFrame, while a second is working (in IOS).

I have the following message error: webPageProxy::didFailProvisionalLoadForFrame: frameId = 26, domain = nsurlErrorDomain, code: -999.

I have implemented both answer from stackoverflow: Ionic iframe loading not fully working on iOS iframe is not working in iOS (ionic framework)

Plus i have sanitize the url of the iFrame. Nothing seems to work, the iFrame is white.

The url I am passing (in case it is working:) https://preprod-tpeweb.paybox.com/cgi The url I am passing (in case it is not working https://secure-test.dalenys.com/front/form/process

These two urls are from action POST form, with an iFrame as a target.

Do you have any idea what to do ? Would it be possible that the host has badly set its website ?

Would it be possible that it comes from the fact that the iFrame has this error: Indicate whether to send a cookie in a cross-site request by specifying its SameSite attribute ?

update: We had the following error: “Refused to load https://secure-magenta1.dalenys.com/front/form/process because it does not appear in the frame-ancestors directive of the Content Security Policy.”