Problem solved.
I am working on a site that does not yet have a domain name assigned. Instead, I am using a ‘number’ IP address followed by a sub-directory name.
The problem arises when UM modifies the sub-directory name in the URL to lowercase. The solution was to reinstall into a sub-directory with an all-lowercase name.
This was a pain in the butt and a big waste of my time. Maybe UM should be fixed so that it doesn’t mess with directory names.
Cheers