Paragraph 13 of the MOU is :
13. After signing this MoU and subject to the beginning of the implementation of Paragraphs 1, 4, 5, 10 and 11 of this MoU and the continuing implementation of these measures, the United States of America and the Islamic Republic of Iran will start negotiations regarding the final deal exclusively on the other paragraphs.
So the next step depends on Paragraphs 1, 4, 5, 10 and 11 being ticked.
1 is the termination of hostilities on all fronts, inc Lebanon.
4 is removal of the US blockade against Iran.
5 is the SoH open by Iran and Oman.
10 is waivers stopped against Iran exporting oil.
11 is release of frozen funds to Iran.
It's right there in black and white, signed by Trump. The ball is in Trumps court to deliver those items specified in para 13, before they even get to the nuke talk.
This is Trump's MOU deal. This belongs to Trump. He used his art of the deal to formulate it and get agreement. This is what Trump says is better than the JCPOA. And if Trump does not deliver in para 13, the MOU fails.