ITR Revision suggestion reqd.

A taxpayer filed their ITR-3 for FY20-21, incorrectly entering rent for a self-occupied property. This led to an incorrect tax demand under section 143(1), even after a rectification attempt under section 154 failed. The deadline for revising the ITR under section 139(5) has passed, and the portal is not accepting the JSON file. The user is seeking advice on how to resolve this demand notice.