E file rejected

First time using Turbotax Home and Business.  A very nice product.  E filing of Federal and State tax returns and both have been rejected three times.  Filed paper copy of 2019 Form 1040 in late Sept 2020.  Always extend tax returns while I wait for K-1's.  Maybe late filing affects the reject??.  I am sure I entered correct 2019 AGI and tried using 0 AGI.  Any ideas?  Thanks.