You need your 2020 AGI to e-file your 2021 return.  If all else fails, trying using a Zero for your 2020 AGI.

How to Find Your Adjusted Gross Income (AGI) to E-file Your Tax Return

https://turbotax.intuit.com/tax-tips/irs-tax-return/how-to-find-your-adjusted-gross-income-agi-to-e-file-your-tax-return/L2BNspAbm

I did not know to enter zero for 2020 AGI because the IRS had not processed my 2020 return (Efile rejected so paper filed).  Because of that my 2021 Efile was rejected so we paper filed.  Question:  Should I enter 0 for 2020 AGI and file electronically even if I paper filed?  We are owed a refund.

@VEJTASA  No, you cannot e-file your 2021 return since you already paper filed.  That would delay your return even more because their would be two returns in the IRS (& State"s) system.

While it's not ideal to electronically file after you've already paper filed, and the IRS will ask you not to do this, in all likelihood it will not delay your refund as has been stated.  Why not?  Because odds are that your electronically filed return (if successfully submitted) will be processed and your refund issued LONG before the IRS ever even sees your paper filed return.  When it does get around to handling your paper filed return you'll likely get a letter about the duplicate filing, but other than causing more backups and delays at the IRS than already exist overall, it won't likely cause any real problems for you. @VEJTASA 

@SDun12  Please don't post an answer that is not correct.  Per the IRS:  You cannot e-file a return after you filed a paper return.  Returns have been delayed longer because of duplicate returns being filed.

Thank you everyone for your advice.  The consensus seems to be that since we already submitted a paper copy we should not try to efile again.

@VEJTASA  Yes, don't send in another return.  You can track the status of your return/refund on the IRS website, Where's My Refund.  It can take allot longer to see any information on their website when a return is mailed.

https://www.irs.gov/refunds

I already stated that it's not what the IRS wants you to do - but it is not going to delay a refund right now because the IRS doesn't even know they have the paper return yet.   You can e-file a return after filing a paper return, it happens all of the time.   Not a best practice, but not prohibited and if the IRS doesn't even know your paper return exists, it doesn't delay the refund.  

@SDun12  it is not a best practice at all.  The IRS states if you mail in a return do not e-file another return.  You are giving advice that is not the right advice and you are telling people to go against what the IRS rules are.  Please do not do it anymore. 

If you mail it in and also e-File,  you have filed a duplicate tax return (IRS code 976), and  your tax return goes into a black hole.

You can be sure of that.

IRS currently has 7 million unprocessed tax returns.

The zero did not work, any more ideas before I paper file ?  Thx

It's funny, I am e-filing less these days than 5 years ago because these systems are so messed up now.

My 2021 return is being rejected but I checked the IRS website and my AGI for 2020 is exactly correct.  They had asked to make up 5 digit pins.  Should I have left those blank?  Is that what could be causing an issue?