I am happy to report that the NAS login problem on all the other machines was fixed by following the instructions of a complete uninstall using the Removal Tool, and a fresh install.
However, I am unhappy to report that a new problem has cropped up on 3 of these machine, which use apteryx.com dental imaging software. Malwarebytes is preventing these machines from communicating with the server machine.
Once Malwarebytes is exited, everything then works ok.
Please note that these 3 machines were among the 5 machines that had the removal and reinstall process, and only these 3 use the apteryx.com software.
Again, this seems to me to be similar to the NAS login problem, where this latest version of Malwarebytes is interfering/preventing communication with other devices on the network.