Thanks KC4RAF,
I was thinking it was a generic issue, but it's the BF UV-5R and Win 10.
I did run across some information that helped. The filename MUST not be, "Generic CSV xxx" as the filename to load. It has to be, "Baofeng xxxxxx.img", otherwise it won't upload.
The solution is to save the radio-downloaded file, then open your self created file with your personalized frequencies resulting in two tabs in CHIRP. Copy your frequencies form your file into the new one, then "save as", retaining the first part of the filename.
Thanks for your help!