Please keep the mailing list CC'd.
In a standard installation, the two versions should exist quite happily side by side, though only the latest will probably run due to changes in the config database (that shouldn't be an issue with >= 2.0, only with older versions). I have many versions installed for example, on both Windows and Mac.
A couple of possible issues could be causing this:
- You're using a shortcut that is actually pointing to the older version.
- The runtime has the "path to webapp" setting configured, and is pointing to the old version. Check in the registry for the ApplicationPath and PythonPath settings in HKEY_CURRENT_USER\Software\pgadmin\pgadmin4, and remove them if present.