Intellij IDEA Project view doesn't show structure as it did before.

I've come across this problem a few times myself. What happened is that intellij lost the module in my project settings. Here's my steps to fix it:

File -> Project Structure -> Click on modules (notice empty list) -> Click on '+' -> Click on import module -> Find existing myProj.iml

I also have quite a few IntelliJ projects and also git folders of text files. I found IntelliJ does not always reconstruct the .idea files correctly. However the following methods work for me.

Open IntelliJ in the top folder where there is no .idea folder. Often IntelliJ will just construct a new .idea folder and works.

Copy an .idea folder from a similar project and modify to fit. The xml files in the .idea are reasonable to modify.

Open IntelliJ in the root project level works for me.

I have a mixed project folder tree like the following:

git_root
- proj_android
- proj_ios
- proj_react
  - lib
  - src

My problem is that when I open IntelliJ on my proj_react folder, I could not see my src folder or lib folder. (My proj_react is one level down from my git_root.)

Then I open IntelliJ on git_root, I could see everything. The problem is solved.