After having RESTARTED my MAC, I had the following problem: While my Windows 10 VM was running, Youtube videos in any MAC WEB BROWSERS did not play anymore. I shut down the VM and restarted the MAC WEB BROWSER. Then I restarted the VM. From now on, Youtube videos in the MAC WEB BROWSER are playing without problems!
Hello @PeterA23, please reinstall Parallels Tools by following the knowledge base article https://kb.parallels.com/4841 to reinstall Parallels Tools and reinstall Parallels Desktop account.