When I wanted to install new or update available maps I saw the following error message:
Connect to Wi-Fi network to download maps.
Solution is on this page:
1) Turn off Power saving – Device|Battery|Power Saving. If this is on it will turn off the WiFi when it thinks it is not being used! You can turn it back on when finished the map downloads.
2) In the Map application go to Settings and turn ‘On-line’ on. This seems to turn itself off…
However for me the first step was not necessary.
Whereas restarting the Maps application was a must.