I can't save. Autosave seems to work, and can load autosaved games, but I can't save manually.
What I do is: ESC -> Select Save -> Enter filename - Enter. The Save button doesn't work.

I know it worked in the past, but I hadn't played for some time. It may be related or not, but before I started my first game today, I deleted all old savegames (including all autosaves) manually. Verification was ok, and I don't use cloudsaving, nor can OneDrive interfere.