Queen of Cups was not correct for me for 2 people. She told me the first one will not come back and that he just wanted casual relationships at that time and was out and about dating. He did come back, he was not out and about dating, but had enrolled to study for another college degree, was all too packed up with work and tests and is serious about life in general. In the meantime, while I thought that he was not coming back, I asked QoC about someone else who asked me out a few times and then disappeared somehow. She told me he was went back to an ex with whom he went way back. She was almost right on this one, all right. He was way out of his mind because his mom got a massive heart attack and almost died and was still critical, so the entire family was focused on that, as it happens in such situations. I am sure she is good for many people, but she was not for me.
As for Sincerity, in my case, there was never mention of third parties.
If you ask me, since the split was amicable and there is no hostility (especially if you want him back), there is nothing bad in reaching out to wish him a happy birthday and test the waters. No matter what happens, it is his birthday and you are coming from a place of kindness to wish him well. Nothing bad about that.