Please see this on what AGI to use if you did not file your taxes last year:
https://ttlc.intuit.com/replies/4231698
Also, please see this TurboTax FAQ for steps to fix the error:
how can i get my code from last year because i don't remember it
Here are a few more resources for you to try:
More about how the self-selected PIN is not saved.
Or, you can get transcripts from the IRS. This IRS site provides some more options, too.
AGI matches but no match for spouses prior year ID PIN. Where do I enter that information?