Slitherine

Currently I'm fighting my way through Act 1. Maybe I'm missing something but it seems to me that I cannot upgrade my units except the infantry. Whichever unit I select - the 'Upgrade' button on the right bottom of the equivalent screen is greyed out.

Is this done on purpose? Or is it a bug? My own stupidity? Or Slitherinesque poetry?

Do you have 1.01 patch installed? Main menu must say v1.01 in the bottom-right corner.

Dammit! I completely missed this patch! No wonder, there's no announcement for it in the forum.

I installed it, and now the Upgrading function works. Thanks for the hint, Rudankort!