After reading all your messages, this could be something that Entra ID is rejecting. To know the exact reason, if I were you, I would use cli tool, connect to Prod and then tail the logs, as mentioned here: Connectors | SailPoint Developer Community
You will see something like this(outlined text):
Further, with Entra ID, I have seen that sandbox and prod connectors behave differently even when they are on the same version.