I had forgotten to add that I had also done a hard reset.

But, that's not why I came back.
One more thing needs to be done before City Navigator North America NT 2015.10 can be used in the NUVI 255W.
The new gmapprom.img file on the SD card must be in a folder named: Garmin, then rename the file to gmapsupp.img.
And, the old gmapprom.img must be left on the GPS.

The new map set is now loaded and recognized by the GPS.
It is yet to be road tested.
But, I have faith that all is well and it will work as expected.
Thanks for the help.
When M'Lady gets back she'll be happy.
That makes my life much easier.