I've read all the posts for mac on StackOverflow. Like this...
On Mac OS Open /Users//Library/Preferences/AndroidStudio4.0/codestyles delete disabled_plugins.txt restart Android Studio,
but I don't have a text file named disabled_plugins.txt. What should I do?
On
On a mac, open your finder, type disabled_plugins.txt in the search box of your finder.
On my mine, it was located at MYUSERNAME > Library > Application Support > Google > AndroidStudioxx
Then just remove the line that references org.jetbrains.kotlin
By the way, the Library folder in your home user directory is a hidden folder. If you can't see it in your finder, that's the reason why.
I faced the same problem, and this worked for me: Click on Go then Go to Folder..., will appear to you a small window that asks you to enter the path copy this ( ~/Library/Application Support/Google/) next delete all disabled_plugins.txt lastly Quit Android studio and restart it.