This fixed it!!
I recently did a clean Win 11 home 21H2 build 22000.856 install, and everything went well except for the windows security "action needed" notification. When I opened Win Security, nothing needed attention; however, I noticed the App and Browser Control section was missing. I typed in "App" in the Windows start menu, and the "App and Browser Control" section in system settings popped up. I clicked on it and turned on the "Reputation-based protection," and the "action needed" warning disappeared.