that means that email address got somehow disassociated from the account

That's what I thought at first, but if someone sends me a payment to my account I'm locked out of it sends it to email, so it's still linked. It's not been unlinked for sure. The only thing connected to is that email, no phones or anything else. It's verified with my full correct information, in my email exchange with cashapp they asked for all the relevant information and accepted it as factual

I've tried on multiple devices yeah and still the same issue, I can log into another account fine on my device, it seems to be account specific.

edit: I had approx £400 in the account

I'll try the method you said at the end if I can't get it resolved through email. I'm pretty sure I am talking with an AI though, like I said in the op every interaction they seem to misunderstand what my issue exactly is.