I saw most of the posts in this topic and I was appalled.
The amount of crazy things that the user has been asked to do, including renaming the profile to test if it was not in his profile, regardless of whether he has knowledge and what tools (programs) he will use.
I noticed the same problem in all versions of Opera in both Windows and Linux and even have a topic I opened a few days ago (https://forums.opera.com/topic/23278/none-of-the-versions-of-opera-runs-a-site-with-flash-even-in-the-block-exception-list) and so far no answer.
The fact is that both Chromium (where the Opera engine comes from) and Chrome work perfectly with, and in the case of Google Chrome the site has to be in the flash block exception list.
And this in both Windows and Linux, remembering that Chrome has flash embeded, but you can through parameters instruct it to use an external plugin.
And for God's sake someone there spoke to have the NPAPI flash installed for Opera. Only those who use NPAPI are the browsers based on Firefox!
This is a design flaw.
Neither the exception list work instead work on Chrome.
If it worked until some versions ago and it works in the browser where the engine used by all versions of Opera comes out obviously it would have to work with Opera itself but it is not!
Either the developers resolve the issue or stop using Opera when you need to use flash content.
Trying with a clean profile is standard procedure in browser troubleshooting if the immediate obvious fixes fail. It immediately eliminates problems caused by changed settings or other extensions.
There is another thread with what looks like the same problem here, so perhaps it is a bug in Opera 49.