When attempting to build siege units during a siege, the game displays no siege units available to build. On mouse-over, the tool tip says "Can be unlocked via technology", but siege technologies have already been unlocked.

I ran into this issue earlier in the game before researching and securing the resources to build Mortars as well, but at that point I though it may be due to not researching and having access to the siege unit of the era that the player is currently in. After Researching the siege unit of the current era and securing the required resources, siege units are still unavailable to build.

I also tried restarting the game and reloading, but the issue remained.

Attached are the last two auto save files of this play through.

Hope there is enough here to give a hint as to what is causing this issue. Thanks!

auto-save 376.ctr

auto-save 375.ctr