I can't log in on a new iPad to sync

I'm not sure iOS 12.5.8 will be able to run any recent version of Firefox from the past several years, so chances are you'll be on an unsupported version from half a decade ago which might not be able to connect to the current account system.

If you look for your Firefox iOS version in settings, or visit https://www.whatsmybrowser.org/ using that browser and posting here the shortcode it tells you in the blue header?

Weirdly it says I'm using Safari 13. I'm in Firefox for sure. The blue line URL is whatsmybrowser.org/b/8PVNF

The iPad is older for sure, my Mom passed hers on to me. I don't even see an option to update the iOs.

Thank you for the response.

Ah that matches with the other details — I realize the user agents get confusing, but specifically iPads trying to enforce a "desktop experience" report as something else, in this case it's approximately the underlying system version.

That said this user agent data matches unfortunately with the iOS version, being Firefox v108 or older from circa 2020–22 that supported iOS 12 back in the day (so the device is probably something like the first iPad Air or iPad mini 2/3). The last Firefox to support such device was probably v38.x in 2021, as the next one: https://www.firefox.com/en-US/firefox/ios/39.0/system-requirements/ specifies iOS 13+ … I'm afraid such an outdated version won't be able to exchange secrets with the accounts functionality to sign into Sync in any meaningful way:(