Didn’t file for years, I filed a nonfilers form for stimulus payment 3/15 then tried to do2019 taxes last night. Now it’s saying my ssn has already been filed, help?

When you filed for the stimulus you were telling the IRS that you would not be filing a 2019 return. Filing for the stimulus, as a non filer, is the same as filing a tax return. You should have filed your taxes to get your stimulus, because evidently you are a filer. Just call the IRS and explain to them that you filed for a non filer to get your stimulus, but now you have to file your taxes for 2019.

If you submitted the non-filer form, it was processed by the IRS as an original filed return with 0 income.  Any subsequent filing cannot be filed electronically; it has to be mailed in.

You have three options to correct this:

1. If you amend your return with a Form 1040X it will be processed like an amended return. 
2. You don’t need to fill out the 1040X to get your return processed.  All you need to do is indicate in a cover letter to your 1040 that you filed a return to get the stimulus check and that this is a corrected return.
3. Or, you can just write ‘1040X amended return’ on the top of the paper 1040.

It's impossible to get the IRS on the phone and the mail-in option is a joke the IRS will let you know that they are not processing any mailed in returns

Mailing in your return is the only option.  If you finally get someone on the IRS phone; that's all they're gonna tell ya.

For details, see:

https://ttlc.intuit.com/community/taxes/discussion/accidentally-filed-non-filer-how-to-fix/00/1527939