Hopped on to file and saw that last years return was rejected , how can I find out rejection code ? Fix when its asking me to file this year ?

You can print and mail it now.  You should have got an email with the rejection code.  Do you still have old emails?  Check your spam folder.  Are you sure you didn't file 2020?  Did you have a refund or tax due you never got?  

Then to efile 2021 enter 0 for the AGI since 2020 hasn't been filed yet.