Mrs ZFT had a similar issue although I’m sure unrelated to your problem recently following a UK visit. Turned out someone had installed some BT software to access a BT system. (Don’t even try to 2nd guess the reasons!!!) When trying to access any other WiFi it was looking for either a 6 digit or 13 digit WAP key irrespective of whether a secured or unsecured network.
No matter what I did I, removing all BT stuff etc, just couldn’t get it to connect to any other WiFi connection. Eventually bit the bullet and Format :C