Hello, I’m Nathan, and I’ll be assisting you today. My livelihood depends on your positive feedback, so your satisfaction is my highest priority.
Sorry to hear you’re having trouble.
It sounds like you've got a problem with the trunk line programming in the pbx system OR there is a fault in the wiring to the pbx (something may have come loose, etc).
As an initial step, you can unplug power to the pbx server for 5 minutes for a soft reset.
If that does not help, the next step would be having a panasonic installer/tech come out to reload/reprogram the system. They do this with special admin software on a laptop. A reprogram of a 4 line system would typically be about an hour job and an average labor or service call cost of around $100. If you'll let me know your zip code, I can help you find a suitable nearby tech.