Cannot shoot infestation (Hastur 1.20.1, macOS, Steam)

I can’t shoot the infestation, even when my aiming reticle is on the infestation through the hole in the wall (made with a HEL II canon).

When I click on the mouse button to shoot the infestation, nothing happens - the (sniper) gun won’t fire.

The attached screenshot may help.

it shows that your soldier has no line of fire, try manual shooting

There was LoS as the reticle was on the Corruption Node. It’s just that clicking on the mouse did not fire the weapon. Weird.

One thing I did not mention was my sniper was standing right next to the hole in the wall made with a HEL II cannon, and the sniper’s weapon refused to shoot.

He was able to shoot after I moved him away from the hole.