Oh Africa!!

When I input major Malian or Mauritanian cities on my route like Bamako or Kayes, Mali or Nouadhibou or Nouakchott, Mauritania into the VISA ATM locator I get "No ATM locations were found within 60 miles/100 kilometers based on your search. Please try another search." but when I input Senegalese cities it finds ATM's.

Is it possible that ATM's that folks saw in times past have been removed or deactivated? Is it possible ATM's that folks saw were merely locally accessible ATM's that could not be used with a foreign bank card?

A lot of things change very quickly and some slowly in Africa and most things are possible- even the impossible!!
ATMs in
Morocco = all over
Nouakchott = yes and they take Visa
Bamako = ditto

Visa is the way to go in Africa.
Speak to your bank before you go and make sure you have the correct telephone number (aka test it before you leave!) to reach their Visa dept.
Automated bank security systems will automatically block your card if they 'see' an unusual withdrawal -aka- from a place not associated where you normally take money out. and, despite your conversation with the bank you will have to speak to them. Also having 2 different visa cards also helps.

Best have some euros in your pocket, an unlocked phone to take local SIM cards and a few £'s credit on your Skype account can also help.
A gps helps you locate banks etc