Hello Jo3ph,
Thanks for choosing the Apple Support Communities. We see you're having trouble with Picture in Picture using your Mac. We have a few steps that may help resolve the issue. Try them below and let us know if you have any questions.
Play web videos in Safari on Mac
"Play a web video with Picture in Picture
- In the Safari app
on your Mac, navigate to the web video you want to play. - Click and hold the Audio button
in the Smart Search field or in a tab. - Choose Enter Picture in Picture.
- You can drag the window to any corner of the screen and the window stays put, even if you switch desktop spaces. You can resize the window to see more or less of what’s behind it. Click the Close button
to close the Picture in Picture window."
If this doesn't work, try testing again with any video extensions or plugins disabled. If issues persist, test in safe mode and see if it works there: Use safe mode on your Mac - Apple Support
Safe mode will help rule out third-party apps as the cause and isolate the issue.
We hope this helps.
Cheers!