I have the same issue, however I submitted the form over 5 hours ago and the trigger hasn't run. I've tested multiple scenarios and the email only triggers if I make a save to the flow, or toggle it off then on. It then sends an email, but this only triggers for responses made recently (within an hour or so), one made several hours before didn't send an email or have any record in run history.
I can't find any known issues with this but it clearly isn't reliable. Can anyone offer advice to help get this working?