Hey @Bosniarat and @sparxef - thanks for the report, first I've ever heard of this type of issue. Sorry that it's not working correctly :(
You're correct in that there aren't any options / settings for mapping the mouse buttons - but it's really weird that they wouldn't be working just during gameplay (but do work on the Main Menu?) Looks like you're running the game in windowed-mode, correct? I'm assuming you can at least see the mouse moving around during gameplay, just that clicking doesn't do anything?
Apologies for the slew of questions here...
Do the keyboard controls all seem to work?
Can you click on the flashlight icon up in the top left of the HUD, does that do anything?
If you walk up right next to a big rock or plant, and hover the mouse over the rock/plant, does the mouse cursor turn orange/yellow instead of gray?
I'll have to look into this more.