Just check the phone itself is able to email in and out and is connecting to internet.
Are you using Apple Mail app for normal emailing?
In iReal Pro, is the forums window is active (it should be if you have internet connectivity) and does the email prepare itself with the backup and you can address the email?
What happens when you press Send? Is it stuck in your Outbox?
Is the upgrade you refer to, iReal Pro updating (from which version to which version) or your OS?
If your OS, there might be settings to check to make sure it is connecting and your email settings (SMTP) are all working correctly (they should be, but probably need checking).