In my case, the simple was simple and the cause was stupid. Mentioning it in case it helps someone else.
A new client gave me his login to audit his site. This worked fine.
Later, he set up an admin login for me in his site. He didn't assign me a user role. This caused the error.
He then changed his own password so I couldn't log in with his account any more. This also caused the error.
Conclusion: the error was legitimate. I wasn't providing correct information during login.
Please follow instructions in the video provided in this link. Worked like a charm for me.
greetings I have this same error please help try everything and nothing works my email is firstname.lastname@example.org
Magento 1 or Magento 2 in forgot Password after login in admin panel
Check your 'admin_role' db table data against a backup. The data in mine got erased due to a db server crash. This was the only way to resolve this issue for me.
Thanks. After trying everything else on this forum post, your solution worked first time.