US-Iran Sanctions: Undoing The JCPOA?

The US Iran Nuclear Agreement Review Act (INARA), enacted in May 2015, calls for the president to issue a certification to Congress every 90 days regarding Iran's compliance with the Joint Comprehensive Plan of Action (JCPOA).  If the president fails to issue the certification, INARA provides an expedited process for re-imposing US-Iran sanctions that were lifted under the JCPOA. 

President Trump declined to provide the INARA certification that was due on October 15, 2017.  So, what happens now?

Must Congress take action under INARA?

No.  Congress is not required under INARA to do anything.   Indeed, given the current US political divides, it is entirely possible that Congress will not act.  INARA simply provides a means for expedited consideration by Congress of "qualifying legislation" should it be introduced in the 60 calendar days following non-certification.