I linked my Facebook account with my Quest. I've since deleted that account. I now have a new Facebook and I've linked it with the Oculus account on PC. The mobile app still wants me to sign in with the Facebook that no longer exists. What am I supposed to do about that?
on your phone sign in on facebook the correct account. if needed log out and delete app data before logging in. Also check email address. Oculus may need to update to the address of the current facebook account you want to use.
So on the web check the below link
make sure the new facebook matches the email in that link
update if needed.
and completely log out of everything on the phone (even facebook web and app)
open the oculus app
merge with facebook it will ask you sign in to facebook and sign in to the correct account.