Are you on a pre-existing sub? Or paying sub month to month? Pre-existing meaning paid sub that has 4 months attached to it as a package deal?

A few steps you need to ensure:
1) No active quests for Grand companies
2) No leves active
3) House/Apartments may be destroyed in the process or as long as you have them active, may not allow them to move

The easiest way to tell whether you're outside of 90 days or not is on the mogstation logged days under your subscription. Does it say 90+?