Can I file last year's return electronically? Not sure how I missed it but, it says it was rejected.

No it is too late to file a 2018 tax return electronically. You will have to print and mail the 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)

A 2018 tax return can only be printed and mailed, it cannot be e-filed.

 

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.