Using the tools>import is safer. Thunderbird needs to know the exact name of the profile and it's likely not the same as the one thunderbird is wanting to see -- unless you copied the thunderbird profile intact from old PC.

Thank You david. It was, indeed, "tricky" trying to get the files from the "backup drive" into the Profiles folder. Apparently, something changed during the copy/paste routine that the newly downloaded TB file did NOT like. Tahnks Again for all your helpful posts herein. They have been quite helpful during this "trying" experience.

Note you will loose ALL passwords using import. (I just learned that myself even though the bug is a year old.)