And there you have it. Happened to me in exactly the same way.
For gods sake don't even think of going through your devices in the belief that it must be something wrong your end !
You end on Performs naughty step asking them to reset your account.
That experience a few times caused me to...
Except it's nothing like that as there no registering of devices. Doing so would mean Perform have a sensible modern rights policy and the technical means of doing so.
I've been locked out using 2 devices, logging in out trying to get the sodding thing to work.
... And not simultaneously.
This in itself is a major problem. The advert on the main site citing "multiple devices" should contain a warning.
Access your account on two or more of your devices (note use of your) during a game and Perform lock you out
Since it take them ages to respond, the game (literally) is up...