I saw the problem you have to log out of your other device make sure you sign into the exact same Gmail account and then set Opera as your main browser and take off ad blockers and everything else until they connect

I've solved the connecting devices to the flow you have to make sure that you set Opera as your main browser then you have to make sure you're on the same account you have to log out of your device then sign into the same Gmail account that's on the flow and it did it after about an hour and a half it finally did it Connect to flow