We are aware of the issue where games won't load and we are (very!) actively trying to figure out why this is. As it doesn't seem to affect everyone we need to narrow it down and that's what we are currently working hard on.
For now a workaround has been identified and we encourage everyone that has problems with Cities: Skylines to try them.
Change screen area to MAX (System > Display)
Start game > Options > Misc > Set screen safe area to max