I have tried to create some basic data to generate a map and I simply get a white box. No sign of a map although I can make a legend appear / change to a bar graph no problem.
I have checked our proxy settings and firewalls and cannot find anything getting blocked - I've checked access to the sites listed in the MS documentation (several places but originally found here : https://docs.microsoft.com/en-gb/power-bi/visuals/power-bi-map-tips-and-tricks).
Have upgraded from March 2018 to Aug 2018 PBI desktop (for Report Server) and no change.
My last ditch effort was to publish to PowerBI and it worked perfectly with no changes.
I have tried turning on logs and found nothing looking like an error, tried bypass geolocation cache and no luck.
Clearly something is stopping the maps loading but I haven't got a clue where to look next so any suggestions gratefully received!
..so update, I've just updated my Report Server to the same version and the maps work perfectly there too - seems it is just a problem with the desktop software, not ideal but at least manageable, would still be good to resolve!.