Thanks OT,
As far as I'm aware my photos on my ex hd are not "in" a Time Machine backup; TM is just the auto program that backs up all my files and photos to my ex hd. What seems different to me as of late, than previously when I had no problems (late 2016-more recently), was that the Photos App on Mac was not trying to open my backed up photos on my ex hd. Or, if it was it was not trying to import them to view them? I don't recall the Photos App being involved like this? Is there another App or manner to open my backed up photos? Perhaps, it is the format that they are automatically being backed up in that has changed now too?
I'm not sure; I just can't access them. I have two older Macs (2009 and 2010 models) on the ex hd with photos files that I cannot access now, nor can I access a 2016 model from itself nor from a new 2018 model. Previously, I could access them; I'm uncertain at what time I could no longer, but it came to my attention recently when I was setting up the new 2018.
Thanks for any input!