On several machines, all Windows 10, all developer machines (.Net, NodeJS, etc., etc.), after installing pgAdmin v4.28, the application will not load. Can access same local PostgreSQL database (v9.x) using Azure Data Studio or with pgsql without issue.
Changed HKEY_CLASSES_ROOT\.js\ContentType to text/javascript as per googled solution, but no joy. Restarted computer (overkill I know but ...), again no joy.
Removed v4.28, installed version v4.26, now I can continue working. But ...