If it is shut and won’t open when you depress the button, the pawl is not engaging the latch. This may be due to the pawl being rounded off, in which case you are hosed and it will have to be drilled, or maybe a locksmith could get a with a skinny tool and release the latch.
Other possibility is that the cylinder is not fully unlocked. Try to spray some lubricant like wd40 down in the lock and work the key. The key should turn easily and you may luck out.
Your problem is not due to the plastic piece that breaks easily between the actuator and the pawl. In that situation the lock actuator won’t work with the key remote, but the box lid will unlock with the push button. That is an “easy fix” , but obviously the box has to open to repair it. Lots of stuff on YouTube about it.
Work some lubricant in there and see if you can get the pawl to turn...good luck
Sent from my iPhone using Tapatalk Pro