Are you sure you’ve been “banned?”
I’ve been the female friend. We were friends for years, dated very briefly, and then stayed friends for years again afterwards. We went on holiday together and hung out loads. My boyfriend (now husband) never cared because he trusted me. And he was right to - neither my friend nor I had feelings for each other or did anything. A brief period dating within a 15/20 year friendship makes him my friend, not my ex.
What damaged our friendship was a new girlfriend. She was jealous and difficult. We would meet, including with my long term partner there, and it would seem fine. But then they’d get home and she would get upset with him about the oddest things. She didn’t like how successful my career was. She didn’t like the fact that I was a good cook so wouldn’t cook for him in case he compared it. She once cried in the loos at a bar because I had said that I believed in something, politically, that she didn’t. It was, frankly, insane.
I tried so hard to be nice to her, include her in things, I even suggested just she and I go out. But it never really worked and in the end it was too exhausting to see her. I never “banned” her, but did start refusing to meet with them because I was walking on eggshells all the time. The mad thing was, I quite liked her, apart from the bizarre behaviour!
In the end, I backed off massively from the friendship. I lost a lost of respect for him for putting up with what was obvious nonsense. We’re still mates, but not that close and rarely see each other.
I’m not saying this is you, OP. But it’s worth considering the other side.