But I don't know how. I was busy establishing a new user id, switching back and forth between the old and new and occasionally rebooting when, on reopening as the original user I received a message something like, "The system has received a request to disable slow keys .... ." I told it to go ahead, and the keyboard function is now normal.
If I had initiated such a request, I had done so quite some time earlier. I am a non-techie but a long time user, I have no idea why the delay or exactly what I had done to resolve the issue, except to disable the slow key function.
Thanks for suggestions.