I’m much happier today. I’ve solved a couple of issues, including the one I initially posted about, and my system is up and running now as it should - with all guest codes working.
The resolution to my initial problem, the guest codes not working, was resolved by plugging my laptop directly into the Base Station using a cable. Logging in to the system while directly connected to it, surprisingly enough, did not require an emailed verification code. When I re-entered the guest codes with my laptop directly connected to the Base Station got them all working correctly except one. That was the second problem I had to resolve.
After trying several different number sequences, it was apparent that something else was wrong. Having known the neighbors for many years, but not knowing their last name, I had entered them in as “John and Mary” (not their real names), and using three words was the only difference from the rest of the guests in the system. I deleted “John and Mary”, and set them up again as “John Mary”, which resolved that issue.
So apparently the system won’t work correctly with a three-word name. That should be corrected, and the User’s Manual should be edited to address using the included cable to connect directly to the Base Station if programming problems are encountered.
Thanks again for your input, and I’m glad that I’ve got this finally straightened out.