Filing the wrong year

Which tax program did you use?

Are you not a tax professional?  How then were you able to e-file with PTO?

It should be clear to you whether you're preparing a 2019 or 2018 return.  There is no mistake about it and PTO will not mistake a 2019 return for a 2018 return or vice versa.

In case you did make a mistake and a 2019 return was e-filed with PTO (which is the big question), your only option is to amend the 2019 return and prepare/file a proper 2018 return.

[Edit: Reversed years]

Yes, seek the help of a professional tax preparer to unwind the mess you've made.

Who are "they"? If  you look at the pdf copy (you should always keep a pdf copy), what year is on that tax form? 

If your perception is correct, you will need to file an original 2018 (you should be able to do that with PTO).

You will also need to file an amended 2019 tax return, which will have to be a paper tax return. https://proconnect.intuit.com/community/help-articles/help/how-to-amend-an-individual-return-1040x-originally-prepared-in/00/4998

Like old age, preparing taxes is not for the faint of heart!

You asked this question in a forum meant for How To Use the professional tax preparation program that you would use to prepare your clients' tax returns.

You will find the TurboTax community is a better resource for personal tax and IRS issues and updates:

https://ttlc.intuit.com/community/discussions/discussion/03/302