I have a problem in inbound calls. 2 of 4 lines answered by issabel but 2 of them dont. It’s while in outbound calls there is no problem and 4 lines work respectively. why and What’s the solution?
You have only told us what the issue is without describing anything about how the device is configured, to what is it connected, and if the telephone provider has busy call forward (rollover) enabled such that if a line is busy and a caller uses that same number to try and call, does the provider see the attempt and roll the call to an available line?
Without knowing to what it is connected, we have no idea how it needs to be configured to satisfy the device.