This issue is similar to Locked out of my Matrix account on mozilla.modular.im / chat.mozilla.org
I noticed that I couldn’t log into my Firefox account anymore, because for some reason the password didn’t match what I had in my password manager anymore and unfortunately, also my recovery key was too old. I was still logged in on two devices, but I could only extract OAuth tokens from the local password store, which didn’t help me. Therefore, the only way to restore access to my Firefox account was to reset my data, which wasn’t a big deal, since I still had everything sync to my Firefox instances.
Unfortunately, now I cannot log in to Matrix / Vector IM anymore. I am still logged in on two devices, so I still have control over the Matrix account, but I cannot log in via SAML on a new device. If I try to do that, I only get a prompt to choose a username, but I cannot choose the one I already have. The other way round, I also cannot reconnect by adding a new email address in the Element settings. If I try to do that, I get an error that the identity provider returns different information than when I first logged in.
Is there any way you can reconnect the accounts? I can prove ownership of both my Firefox and my Matrix account.