ScubaPro did follow up with me. They suggested this:
[I suggest downloading the latest version of Smart Trak from our website if you haven’t done so already. If you are using an old version or one from a CD you will encounter some issues.
Once downloaded open it from the start menu the first time, not the shortcut. We are not sure why this works, but after the first time opening it you can use the shortcut.
If this does not correct the issue let me know and we'll explore other causes.]
I tried that, with all manner of uninstalls first, INCLUDING going into the [Registry] and removing all traces of Smarttrak. It didn't work.
I tried installing it on a 'clean' version of Win10 1703 > didn't work.
Scubapro sent some instructions to change the [Permissions] for Smarttrak. That didn't work either as I was already logged in as an [Administrator], and had tried also loading Smarttrak via [Run as Administrator].
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Having tried all the usual routes, I took a long approach and it appeared to have fixed it. No idea why this worked and the direct method did not.
I loaded Win7 on a spinning HD. I activated that. Loaded Smarttrak > it worked. No special 'methods' required.
Upgraded Win7 > Win10 ver. 1703 with a DVD copy. Smarttrak worked.
Upgraded 1703 > 1709 with a DVD copy. Installed all current updates. Smarttrak still works.
Cleaned up the HD, created disk image with Macrium Restore, restored to SSD. Seems to have gone OK. Smarttrak still works.
Go figure.
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This is all pretty much exactly the same hardware, permissions, etc. that have been on the PC all along. The only differences were the initial load of Win7 to a spinning HD. BUT, I did load Win10, both ver. 1703 and 1709 to spinning HD to test (AND the same Samgnsung EVE SSD), and none of those would run Smarttrak afterward. They WOULD successfully run any other software I loaded, so it's difficult to see how either the hardware or OS were the direct problem.