I had this problem after I reinstalled my Opera and erased my user data, I got to connect everything the same way it was before, except Flow. Then I turned off vpn, adblock, nothing worked for me but delete my previous Flow information from my phone and unfortunately I lost many important messages... You have to disconnect both phone and desktop on settings and then delete Flow completely so it'll work I don't know why. When I got my new notebook I had to transfer everything from the old one and I got zero problems with Opera, I've never been so disappointed.