This one surprised me. I am setting up a new computer, for work, and this is a lot more locked down than I'm used to. IntelliJ would not open files with the extension .env, which we use as environment files on certain projects. They are just simple text files and IntelliJ should have no issue opening them. Inside the IntelliJ project explorer, clicking on the files caused nothing to happen.

I would have sworn in the past I had some kind of "open as ASCII" option, but I could not find that. It turns out that my operating system did not know what type of files these were.

I was able to right click on the file, select "open with" and "Choose Another App" and then select IntelliJ", and that opened the one file, but did not allow me to open other files with the .env extension.

I tried it again, and checked the "Always Use this App to open env files" box. Then I restarted IntelliJ and was good to go!

Here is a screenshot

I can't remember ever running into this issue before, so I was a bit surprised.

If you run into it; then than I hope my solution helps.