Through the last several auto-updates, over the last several months, I have noticed that if Aqua fails to make a successful TLS/SSL connection once, it will never succeed again without killing the app and restarting it. (I.e "force stop"). After the re-start, the next connection attempt has always succeeded.
When a connection attempt fails, Aqua displays a grey/transparent window for just a second, full of failure details, that disappears before I can note any down any of the details.
I am otherwise a very happy Aqua Mail Pro user, thank you for it.