Error Message After E Filing - Oops-an issue occurred. Please check back shortly!

[l5482]

I filed my taxes right about quarter to midnight and it seemed to transmit but on main page it says "Oops-an issue occurred. Please check back shortly." There is a diagram showing it is pending and down below it says the federal return is pending but I never got an email and the error message is concerning. Any info?? 

[PaulaM]

This is likely due to the large volume of submissions. You should wait.