Mac logged me out and can’t get back in

Solution 1:

The various options to recover control are quite straightforward to enumerate, and you might have one you think is best to start with:

1. Boot to recovery and reset the password of one or several admin accounts. (Also, you can use Terminal app in recovery to look if your /User folder is intact before deciding what to do.) - https://support.apple.com/en-us/HT201314
2. Make a new admin account, then look / repair / backup / reinstate other accounts. - New MacBook had user accounts already; I deleted admin and can't get back in
3. Bring another OS to the Mac and backup / fix / diagnose. - https://support.apple.com/en-us/HT202796
4. Reinstall the OS and see if migration repairs the account - https://support.apple.com/en-us/HT204904
5. Wipe the Mac and load a backup (easy if you know TimeMachine is ready to go) - https://support.apple.com/en-us/HT204904

Which you choose is mostly up to your skill level and if you know you have a backup - it takes about 10 minutes of time to erase / install then you wait, then it’s 5 minutes to start the restore, and then you wait until it’s done.

The other options can take far less time once you know the steps, but for some take a bit of learning in terminal and could end up with data loss if you don’t just back things up first.