As Lucidique stated, its a Funcom Live Service thing. More specifically a Microsoft Playfab thing which FLS ties into. Playfab not only doesn’t really support offline authentication, but even recommends developers do not do so for security reasons.
I’m not suggesting I agree with that, I’m just saying what I’ve seen on questions and troubleshooting I’ve seen involving Playfab and the responses given from Microsoft reps. But whatever system Microsoft uses for Playfab doesn’t make it easy.