Clearly, it wasn't working if they needed to hide their activities in underground bunkers. The plan for the Iranians has always been to buy time and obtain sanctions relief while secretly using the money to fund nuclear technology and build missiles. The only durable solution here is the collapse of the terrorist regime and disarmament of the county.

It was working, as US intelligence agencies testified to in congress as Trump ripped up the deal. Then trump put heavy sanctions on them and they restarted their enrichment program.