Trouble accepting a Family Sharing invite

Hello,

My dad sent me an invite to join his Family Sharing group on Apple, but I can't accept the invitation. Every time I click the link, I just get an error that says "There was a problem loading this page. Try again or come back later." Trying again & coming back later both reliably produce the same failed result (as I have, unfortunately, confirmed through rigorous experimental trials [and tribulations]).

I've contacted the Apple Support chat a couple times about this issue, but they seem to get snagged on the fact that I don't have any Apple devices. But I do have an Apple account, and my sister was somehow able to accept her invitation without using or owning an Apple device.

I have tried accepting the link across multiple browsers & devices, resending the invite link, sending the link via text message & email both. I've even tried accepting it on my dad's iPad, but since it's associated with his account, it either thought he was trying to accept his own invitation, or I used a private tab in a non-Safari browser & just got the same error page.

Has anyone run into this issue, and is there a workaround or solution? I've included a screenshot of the error page, although it's hard to imagine a less helpful error page.

Any help would be much appreciated. I'm pretty much stuck at this point, and if I have to enter many more 2FA codes I fear my soul will wither to a point where I may no longer be capable of enjoying the services the Apple platform offers.

Thanks,

Nash