The PTR and Beta aren't set up to interact with the token system (tokens going to your Beta/PTR accounts would be a waste of faux gold not to mention the other end getting faux gold for their faux token that dissapeared with the Beta
) so C_WowTokenPublic.GetCurrentMarketPrice() is just returning nil, nil. The addon may just be failing silently due to this or, there may be a "service not available" message somewhere.