The following URLs, just used to work (replace KEY with your API key):
https://open.mapquestapi.com/elevation/v1/profile?key=KEY&shapeFormat=raw&latLngCollection=41.222%2C4.33
I also tried this one:
https://www.mapquestapi.com/elevation/v1/profile?key=KEY&shapeFormat=raw&latLngCollection=41.222%2C4.33
Now it redirects to: https://developer.mapquest.com/documentation/
The MapQuest development team rolled out updates to our full suite of APIs and mapping tools. The open geocode, directions, guidance, mapping, elevation, and Nominatim APIs reached their end of life and have been shut down.
The Open Geocode v1, Directions v2, and Static Map v5 APIs can be replaced by their licensed counterparts by replacing the open.mapquestapi.com base URL with www.mapquestapi.com with little or no code update. Open mapping tools can be replaced by their licensed versions. The current JavaScript SDK is MapQuest.js (https://developer.mapquest.com/documentation/mapquest-js/v1.3/).
While notifications of these sunsets were sent to most MapQuest API users, some free accounts were not able to be contacted earlier, so we apologize for the lack of notice. We regret any disruptions this may cause.