I've been following the Mendix introduction course for a couple of days, and it was all working perfectly. But since this morning, I'm not able to use the 'run in sandbox' feature anymore. I also can't press the 'view app' button next to it. I can still acces and run the latest version I uploaded via the mendix launchpad. I don't recall doing anything that didn't follow the introduction course that should effect the program this much. I've also tried creating a new project, but again, no possibility to run in sandbox. Help would be very much apreciated. Thanx, Jan.
It was a temporary issue. The Run in Sandbox button should be active again.
Reopen your project and try again.