Error: The subscription server response is invalid

If you encounter this error message, you can easily fix this by signing out of SketchUp, restart and sign back in again. 

1a. Click on the profile icon at the top right corner, then "Sign out".

1b. Alternatively, if you have a file opened, you can access the same on your toolbar.

2. A web browser page will open confirming that you've signed out of all things SketchUp, relaunch and open the "Welcome to SketchUp" window, and click "Sign in".

Sign in with your Trimble ID and associated password. You should now have full access to SketchUp and Layout again.