ADDENDUM:
In addition to the information above, if you owe Federal taxes due, be aware that time is growing short to get this issue worked out before additional penalties.
If you are due a Federal refund, there is not a penalty for a late Federal return. On the other hand, if you owe Federal taxes due, you could end up with both a late filing penalty and a failure-to-pay penalty if it continues to reject and you go past the date to timely postmark a paper return. The IRS says:
"To timely file a paper return after an electronic return was rejected, your paper return must be postmarked by the later of the due date of the return (including extensions) or 10 calendar days after the date the IRS gives notification that it has rejected your electronic return."
https://www.irs.gov/faqs/electronic-filing-e-file
