@dave r said:

Unfortunately you failed to answer my question about how you are attempting to install it. Please tell us HOW you are installing them. And give us the exact text of the error message you are getting. Help us help you.

I also have this same problem and error- install through sketchucation extension manager 3.0, sketchup pro 2016, windows 10 Pro

The sketchucation manager shows they're installed, but no drop down in windows- extensions, and no toolbar.

There are other extensions downloaded through trimbles extension manager in the same plugin folder that work fine, so it's not the location.

Thanks!