I've had a lot of progress on this thanks to the feedback I've received from the community, but now I have two problems with my model.
One is that kids seem to not be entering the system (PCIs 87-114) for some reason. If I simply remove the rest of the PCIs, the model does indeed simulate children arriving.
The second problem is that patients are stuck in the optometry chair for the whole simulation. I have checked to see if my predecessors or next activity have problems, but everything seems to be fine.
I would greatly appreciate any help.