I would double check the install path for GWX.
If it's not pointed at the EXACT path it will throw that error message.
Even with a squeaky clean install.

Finally got GWX 3 installed again. Very relieved.

I would just like to get some clarity regarding the late war sensors mod. The manual states, paraphrasing, in 2 points that:

A. You should enable the mod for Type VII and Type IX boats, then not touch the sensors during outfitting.

B. If it's the type XXI everything is done automatically.

What I need clarity on is this; should you only enable the mod if you are driving a Type VII or IX? Or must you enable it if you are in the Type XXI too?

SH3 Commander
 

Is there a way to get this to work with sh3 commander? I still seem to get radar destroyed after following the instructions. Indeed is there a way to save before mission starts?

As you rightly noted, this applies exclusively to Types VII and IX.