After last update most of northgard achievements icons in galaxy turned into placeholders for me. There are a few achievements not affected by far most of them are like this.
I cheked other games I own on GOG and their achievements are showing correctly, so I assume this is something Northgard devs broke with current update.

How long has it been since you reported this issue? I'm also having this problem right now. Well, in my case I can go to overview and only find the most recent achievements activated but not all of the ones I've earned so far. Especially obvious with the Lion kingdom's achievements Do you have a moment to talk about our Lord and Savior? and Everything the light touches. I have to check the list thoroughly to see if there are more not being activated as expected.