The May 12 deadline is when President Trump would have to extend sanctions relief from the deal. Without that, the US would effectively be withdrawing. Iranian officials have made clear if that happens, they’ll resume uranium enrichment they’d stopped under the pact.
The three EU parties to the deal have been trying to come up with a sideline agreement with the US to prevent all this. So far, President Trump appears unwilling to budge. French President Emmanuel Macron appeared to join Trump in opposing the deal’s continuation, backing a joint statement from the two calling the current deal “insane.”
If this is actually Macron’s position, it’s a dramatic change. Previously, all other P5+1 parties and Iran supported the deal as written, and viewed it as working very successfully. The US was the only nation where substantial opposition existed.
Iranian Foreign Minister Mohammed Javad Zarif was unimpressed with the US threats to withdraw sanctions relief, noting the US has been violating the terms of the deal in any case. Iran has ruled out renegotiating the deal to give the US what it views as more favorable terms, again, on the grounds the US wasn’t respecting what they’d negotiated in the first place.