I’ve just had the same message. I used AdBlocker in Chrome. I have it permanently paused for flightsim.to Now, even with ads permitted and AdBlocker paused, it will not let me download.
Happy to see ads. Happy to pause my AdBlocker. Not happy to remove it entirely from Chrome because of something flakey in the .to website. As for going Premium? Yeah, right!
UPDATE: I emailed flightsim.to support and had a response in less than 20 minutes. It turns out that DuckDuckGo privacy essentials extension in Chrome was also functioning as an adblocker. I pasued that and problem solved. Looks like they just closed up a loophole. I’ve no problem with that. Impressive support response by flightsim.to