How can I fix error "ApplicationException: Unable to find a suitable compiler"?

Last night, I finished my Unity work. I saved it, closed it, then reopened it and build it, then saved and closed it again, then reopened the build and it worked fine.

Today I cannot find the build anywhere on my computer and it is now coming up with this error message:

ApplicationException: Unable to find a suitable compiler
UnityEditor.Scripting.ScriptCompilers.CreateCompilerInstance (MonoIsland island) (E:/BuildAgent/work/71ca6fec1b41cc30/Editor/Mono/Scripting/ScriptCompilers.cs.101)

I have no clue in which to fix it.

I had some students in my class run into this error as well. What I found was they were creating published builds and saving them inside of the Assets directory. By simply deleting the builds or moving them out of Assets, the errors went away!

Hope that helps.

I had the same problem.
Solution is: Assets → Reimport all.

SOLVED- Solved it by removing a folder that has models in it. Basically solved by removing stuff done/added after a previous successful build.

Well all I can think off this quickly after some google searching is:

1: Rebuild else 2: Reboot +1 else 3: Reinstall + 2 + 1 else 4: Get a better answer than mine which is advice at best