Okay, let's clarify. The Islamabad MoU was signed on June 15. As per clause §1, the parties agreed to end hostilities on all fronts and explicitly in Lebanon. Hezbollah agreed. Israel did not, and continued to attack Beirut every day, with the USA's blessing. The USA could have done any number of things to try to reign in their rabid dog, even something performative, but elected not to do so.
That's the breach of the ceasefire, and it's the background to the other breaches of the MoU by the USA that I mentioned above.