Apparently there was some Win10 update, which made the scrolling with the right mouse button not possible anymore (with 1.7.1). It is possible to fix it with putting scrolling on left mouse button, but that doesnt work with in map overview scrolling.
OpenTTD fixed this issue with 1.7.2. and also with 1.8.0.
Sadly it's not possible to play on CityMania, if you have this issue.