So, I’ve decided to look at GNOME Maps yesterday and found that this happened:

http://open.mapquest.com/ shows the following message:

Beginning July 2016, this version of MapQuest, along with Open.MapQuest.com, will no longer be available. We apologize for any inconvenience. If you’re using a map generated from this site on your website, please visit our Developer blog for information on how to transition your map to our updated tiles.

So now all the tiles displayed by MapQuest are hosted on MapBox servers, and every request requires a key to be provided.

actually we don’t do the maps anymore, we use Mapbox. MapQuest is focusing on some mobile and IoT applications, routing and direction engines rather than maps

– http://stackoverflow.com/a/38356148/340480