Maybe the codes wasn't synced, have you tried going to settings --> Time correction for codes --> Sync now

There's also a freewallet staff here which you can contact: Freewallet (You can either ask him to reply on this thread or to contact you privately)

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But what do you mean by one code for all accounts? do you mean the backup code (16 characters) or the token which you are entering everytime you login? (6 characters)