How many of the portals in the homestead have been opened completely? They get marked on the map after you enter, have the encounter with Astarte or the demon, and then return to the main section of the homestead through the portal (in some cases a main character needs to be selected as leader for that).
If a portal is open but not marked on the map, it means the game doesn't register is as completed, and the next portal will not be opened until it is.
All the portals, except the Forbidden Zone, must be opened before the Source temple door will open.
Is Zixzax standing by a portal or the statue? If you missed entering a portal earlier, Zixzax may be standing around outside waiting for you. If he isn't where he normally is, check around all the unopened portals.
