That happened to me a few days ago. But the latest build fixed it for me.
Discussion
Mm I just deleted and reinstalled the TestFlight app.. tried posting again, same issue :/
It sounds like nostr:npub1l2vyh47mk2p0qlsku7hg0vn29faehy9hy34ygaclpn66ukqp3afqutajft is aware of this bug. But feel free to send additional details.