The account that is created when you enter Euchre.COM as guest player, is connected to the ID of your mobile device.
If this ID number is changed due to:
replacement of the mobile device;
resetting the device (factory reset);
or other reasons.
this account will remain active in our database, but you won't be able to log into it.

This is happening, because your mobile device (new or reset) has different ID number then the one you were using to enter your account. Once you enter as guest with this device with the new ID, a new account is created and it is again connected to this new ID.
To avoid this you must connect your account with your Facebook profile, Google profile or email.