Installed the addon a few days ago, though it doesn't seem to work at all. Tried to upgrade allies in a hotseat match, got some up to lvl 9, with no upgrade showing. Also, there are no upgraded units in Hotseat MP battles.

Tried to -> install / reinstall
-> repair installation
-> installation via galaxy + without galaxy

Nothing worked so far. Anyone else having this problem?

Yes. I've tried uninstalling and reinstalling everything at least 3 times and still no new units.

Sadly, i got no fix for this problem. Did some testing while talking to GOG's Support, then wrote to support@snowbirgames.com about 1 month ago. Still waiting for an answer. Found a thread on
Steam-Forums (from around 2014 or -16, iirc) describing a similar problem, which was later fixed
by a patch (1.4-something? Can't find the thread anymore). If i get a solution, I'll post it here.

Hi. According to a post in another thread this thread the problem should be gone now, it was updated to v1.83.