Heartfelt thanks for this valuable information!
I will be hunting down the my.ini file to set up those changes so they remain permanent.
Turns out that there was an uncancelled shared hosting account with the same domain name I was working with that was pointing to a different IP address, and taking precedence. So, I have instructed to have that old IP changed to the new server's IP. And got rid of the unused hosting account!
This should work now!
If not, I will be back for sure, but I am confident that we have found the root cause for the persistent error.