IntelliJ IDEA 2020.3.1 (Ultimate Edition) U-203.6682.168 - Cannot resolve symbol - Java classes

Question

After update to IDEA 2020.3.1, some of my projects cannot be built successfully in the IDE.

I'm getting

Cannot resolve symbol ''

for classes defined by me. All classes from dependencies are loaded OK.

I'm using gradle wrapper and I've tried several things to fix this issue without results:

1. Reinstalled Intellij Idea. Deleted local folder in AppData\Roaming\Jetbrains...\IntellijIdea2020.3
2. Cache Invalidation from the IDE
3. Deleted.gradle folder with all cached dependencies
4. Deleted project and download again from git repo.
5. Rollback to different (older version of IDE) 2020.2.x

Project is built successfully with gradlew clean build . The only problem is that the IDE cannot find the classes. Some of my projects are OK, but others are not.

Answer 1

I had the same issue (Intellij 2020.3.3) and solved by invalidating caches of Intellij (File | Invalidate Caches / Restart)