Thanks Pascal. Tried it and unfortunately it didn’t change the fact that the Localization folder is missing, which is supposed to contain the material library.
I also ran across this thread where someone was having a similar problem with no Localization folder when they installed Rhino:
…which has this link:
https://wiki.mcneel.com/rhino/installingrhino/5.0
…which I followed, but didn’t have any luck. Still no Localization folder on my computer.
Any other suggestions?