Thanks Mike!
I wanted to find out if the SD just came Un-seated, so I took the SD out of the turned off phone and re-inserted it, restarting the phone.
The phone could not see the SD. I repeated a few times. Still no luck.
To find out if the SD card was bad, or if the phone's reading slot was bad:
I took the SD out of my GPS (the only other micro SD that I had), formatted it & put it in the phone blank. It was seen by the phone.
The phone added many folders to it by itself. (Setting it up, I guess.)
This told me the Slot was OK.
For fun, I took the Phone SD & put it in the GPS. The GPS saw the music on the SD. (That's all it should see as far as I know.)
This told me the SD was OK.
This made me believe that the slot in the phone and the SD card were both OK and something corrupted the SD.
I copied the contents of the Phone SD to the computer. (I do have a recent backup, but wanted today's version.)
I formatted the Phone SD in the computer & put it in the phone. The phone saw it and put some folders on it.
I copied from the backup to the Phone SD any folders that actually had files in them, such as Music, Documents, etc.
Some only had empty folders marked Cache or other. I skipped them.
Next, I put the SD back into the phone and the phone saw it & could read from it.
All of the apps that I had on SD were gone, even if I put their empty Cache folders from the backup onto the SD.
There must be important files in a folder that the phone over-wrote when I put the blank SD back into the phone.
I'll re-dwonload them.
I still do not know why the phone did not read the SD, but now can (after a re-format in the computer).
Do you think it is wise to assume the SD is on its last legs and I should buy a new one?
Or, is there another possibility for why the phone stopped reading the SD, but now can?
Thank You Again!
Paul