Error We're Solving

In some upgrade cases right after the Update you only see an error 500 like this:

This often happens if you've installed 2sxc many times. The reason is that in the Update 2sxc makes web.config changes and comments out the previous settings. After many updates the comments get very long so you're web.config will be more than 250k in size. In VS code the web.config will look like this - you'll see a lot of comments:

Solving the Problem

This is easy to solve: just remove all those comments and save the web.config, and you should be back online.