When the mobile authenticator requires logging in again? [closed]
Solution 1:
We can only guess what happened, it's possible that factory reset counts as transferring to new device:
After transferring the authenticator, any new trades or market listings will be held for a couple of days to protect your items in case your authenticator is ever transferred by a malicious person
Good sources of information could be official Steam Support Articles: Steam Guard and Steam Trade Holds.