The Arbalist+? I'm having the same issue

Yea issue for me too. The recruit button doesn't highlight like the other two units.

I'm quite surprised by how many bugs Ive found in this game.

Anyone ever figure out a solution to this?

I do have the very same issue .. still 4 years later :(

Curses! LoL. Not a bug .. it's a feature.
We already have 5 of those cards since beginning of the game.
And somewhere I just read, you can only have 5 of the same units.

The game should definitely tell you this when hovering over that button. (You can't build more you have enough)
I had to dig external sources to get this knowledge and explanation. Therefore I am writing it here.

Originally posted by Hardcore:

Hey. Super early in the game. Just before the bandit camp near the church. Built the structure so i can recruite units. And I can get some of the lesser crappier ones, but not arbalests. What am I missing? Thanks :)

You are missing nosthing. It's 2024 already and that bug is still present (as well as with some other unit creation< arbalests are not hte only one affected). Shame on devs