This plugin hasn’t been tested with the latest major releases of WordPress is showed up to my WordPress plugin after I did not update my WordPress plugins for a year I think or months and many WordPress version is released after that.
This is the exact notice message displayed:
This plugin hasn’t been tested with the latest 3 major releases of WordPress. It may no longer be maintained or supported and may have compatibility issues when used with more recent versions of WordPress.
How to fix it?
Edit your readme.txt and update the Tested up to: to the latest WordPress version and the current version is 5.3.2
Same changes on your plugin php main code where you can see the Tested up to: along with the Plugin Name, Plugin URI, etc.