Please post a log with your issue! Here's how...
OBS Studio creates a log file each time you run it which contains very useful diagnostic information. Without a log file, it's much harder for any support volunteers to figure out problems and your post may be ignored. To upload a log file, go to the Help menu > Log Files > Upload Last Log...obsproject.com
But this may also be an issue with the service.
You're doing a test stream, so the grey you see is the test data. Add some sources and do a regular stream.