I had a similar odd incident a couple of weeks ago; router seemed sluggish so I rebooted it from the browser window which is not unusual once a month or so.
Inexplicably it seemed to restart as if I'd done a full reset which should require poking a hole underneath so far as I know.
Anyway soon got the connection back and renamed the network same as before but 2 or 3 devices simply would not connect yet others would.
Suddenly remembered I made a backup of router settings about January - applied them and all back to normal.

Moral - backup router settings in advance if you can -  it can be harder than you'd think to get everything happy again.