2nd liens stripped off before law changed in 2015

[Alex Monge]

Does anyone have any info on how can a  2nd lien against a property be removed when it got discharged in a bankruptcy chapter 7 when strip offs were permitted by bankruptcy law and discharege says assignemnt of mortgage/lien shall be deemed void and extinguished because property value was underwater and was zero? This changed after 2015 when no longer strip offs were allowed.  Any feedback, highly appreciaed.