Filings got rejected after I completed according to TT. Didn't know this until 2:40 on 4/16. NOW WHAT? I am freaking out! I did not file for an extension!!

[Rachel_W]

No need to worry! 

You have a 5-day grace period to either successfully e-file or paper-file your return to avoid possible penalties. April 20 is the last day of this grace period unless you're a Maine or Massachusetts resident, in which case you have until April 22.

Also, if you're expecting a refund on your 2018 return, there's no rush. No extension is necessary if you are expecting a refund.  You have 3 years from the return's due date to file and claim your refunds.