Hi, Kauan!
As I understood, your conveyor box isn't accepting more items because the processor output port is closed. So, here goes a couple of options
First, you can put a queue after the assembly line conveyor so your station wouldn't be blocked, and your trigger for open the conveyor output port would work just fine.
Even then, I saw that the conveyor box is blocked because the processor output port stays closed until a iten gets out the station. So, another option is edit your On exit trigger at processor, so it verifies is the source box is blocked. If it is, so the prcessor output port is not closed.
In the attached model, I changed the On exit trigger.
Please let me know if this answer is appropiate for your questions.
If it isn't, feel free to explain more about your model and desired logic.
different-time-on-processor_ANSWER.fsm