Some questions:
- Is it always the same six factions you are still able to access or do they change?
- What happened to the other factions, do they show up as locked on the Underworld map? Please post a screenshot.
- Did you have any progress in any of the factions you are no longer able to access, e.g. Hoard leveled up or Delve runs completed?
Edit: Seems to be an issue with the Hot Fix, see Missing classes - underworld factions - weapons - pets and other features since reset