Sacred Haven of Debauchery

If you have version 1.6.0, then yes, you have a bug. In this version, the AI doesn't declare war at all.

That makes sense. Yes, I have 1.6. Damn.

Added 2 minutes ago
If I install the latest patch and continue my current game, will the problem be resolved?

Added 59 seconds ago
Or is it impossible to continue a game on a different version?