I have also tried these suggestions that I found on another thread:
"Goto https://html5test.com/ and make sure it says "yes" for h.264 and aac. If they say "no", do you have an "N" edition of your version of Windows? If you do have an "N" edition, you need to install/enable the Windows Media Feature Pack. If "yes" for h.264 and aac, and things still don't work, goto the URL opera://settings/system, disable hardware acceleration, restart Opera, try again, and report back here if that worked to trick the sites into thinking you're using Chrome.
Another thing you can try is goto the URL opera://flags/#reduce-user-agent, enable the flag, and restart Opera."