|The drives are not that old. They are only 2-3 years old, at most.|
That two drives cannot be detected at the same time, both before when I had the same problem, and now, eliminates the chance that of that.
And, the 2 drives failed to be detected once before, both at the same time, and then were both detected at the same time when I was able to get them to be detected again. The previous time I did nothing but restart the computer several times. Nothing else was checked or done.