Did you enter 0 for the AGI since you didn't file last year?
When did you file 2019? If it was late in the year or you mailed it, try putting in zero for the AGI. And see, https://ttlc.intuit.com/community/rejections/help/what-if-i-entered-the-correct-agi-and-i-m-still-ge...
How to correct the AGI
If you can’t get it to efile you will have to print and mail it.
How to mail a return from the Online version
Be sure to attach copies of your W2s and any 1099s that have withholding on them. You have to mail federal and state in separate envelopes because they go to different places. Get a tracking number from the post office when you mail them for proof of filing.
For AGI Reject code 031
And being retired doesn't mean you don't have to file a return. Did you have any income? Like a pension or IRA distributions or Social Security or interest, dividends, sales, etc? It doesn't go by age or employment status.
Do you need to file a return?