Disabling the ad-blocker for Deezer's site has worked. Deezer is now playing properly in Opera. Flash ppapi version was installed and up to date, so it was just the ad-blocker causing the problem.
Thank you for your help.
Do more on the web, with a fast and secure browser!
Download Opera browser with:
pasfia, If you are using Windows 10 I have found one way around the problem. Deezer is available as an app from the Microsoft store. However, that still leaves Opera unusable for any other websites that rely on Flash. It is a shame as I would prefer to use Opera exclusively but other browsers have to be kept on standby.