My taxes were rejected and I don't know why. Also, I can't find the option to correct the problems and resubmit. Maybe because it is past the deadline? Please help!

If the tax return was rejected it was probably for the 2017 AGI which is not needed on a mailed tax return.  Since a 2018 tax return can no longer be e-filed then download the PDF so that you can print and mail the 2018 tax return.

To access your current or prior year tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/

Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show.  Click on the Year and Click on Download/print return (PDF)

Print, sign, date and mail the tax return to the IRS.  Include with the mailed return any forms W-2 and 1099 which have taxes withheld.  Go to this IRS website for mailing addresses - https://www.irs.gov/filing/where-to-file-paper-tax-returns-with-or-without-a-payment

There are no penalties for filing a tax return after the due date if filing for a tax refund or there are no taxes owed.