Hi,
Thanks for reporting this issue. How long does it freeze up on your end? Loading the plug-in should not take longer than 1-2 secs.
Also, when trying to load the plug-in, do you see any text in the script editor?
There are a few things we can try.
Sometimes resetting Maya to defaults can help. Here are the steps to do this.
1. Close Maya.
2. Uninstall the ProRender plug-in.
3. Locate your pref folder C:\Users\Name\Documents\maya\2019.
4. Rename the Prefs folder to Prefs_old (this will temporarily back up your old Maya settings in case you wish to roll back to them later).
4. Install the ProRender plug-in.
5. Open Maya, and when prompted, create the default workspace.
6. Try to load the plug-in.