So when the Secret Service detail saw that local LE wasn't complying with their plan they ignored it and let President Trump go up on the stage.
Doing nothing to prevent the shooter from firing is also why the Secret Service failed to do their job. JMO.
The investigation is ongoing and we don't have the details, but I haven't yet seen anything in the photos or news media to indicate the SS saw or had any knowledge that the other LE had deviated from the game plan.