If no addons are listed after verifying the Projects and Filters are set correctly, there might have been a problem when generating the Addonlist- xx .json file generated after updating the collection on GitHub.
Inspect the https://raw.githubusercontent.com/gramps-project/addons/master/gramps52/listings/addons-en.json (or fill in the language code if you’re not running the English version) and see if the file is intact on the server.
If it looks like there’s a problem, let us know.