What is your original email? For my case, it’s an expired domain (actually not yet but unlinked DNS), so the email bounced a few times and basically marked the email as invalid etc.
So since it cant send emails to the old acc telling it “you have added a new email”, then it basically marks the account as dead.
I linked the domain back, and tried it with my other accs, so far 1 succeded. It also sent me email to the domain “your previous email is unreachable”. I used the same domain just with diff alias, so i’m gonna try with other domain and see what it says.
Well you’ve just confirmed my suspicion. The reason is because the email account is invalid so after a few bounces from fb they mark the account as dormant, basically as good as dead.
If you somehow got it to reactivate after the inactive “grace” period, then depending on provider, emails will not receive during the grace period, so even after you manage to activate it back, the emails that’s bounced by fb email is what’s flagging the account.
Like i said earlier, when you add a new email, an email will fire to the old email to notify of your changes. When FB is not able to send the email to the old one, then it will raise a flag telling FB, someone might have hacked into the account to change email. When they occasionally send notification emails to the old email, it would have already flagged the account since their notification emails kept bouncing.
Tried now on a second account to change the mail (where the actually mal adress is still valid) and its functioning. So you are right, when the old mail adress is not valid since a long time anymore then the account seems to be flagged and you can not change the mail adress anymore.