Hello Peter & Welcome to Just Answer,
I'm Greg and will do my best to assist you today.
Sorry to hear of any issue you are having with your phones.
To help you with this issue, may I ask:
1) The FULL Model Number of the phone system you are working with? If this is a cordless system, that model should be printed on a sticker on the bottom or back of the main base unit.
2) What phone service provider (phone company) you have for this phone line?
3) If you have ANY other devices (phones, fax, etc.) attached to this same phone line and if so, are they working properly?
4) Do you have a BASIC corded phone you can connect to one of the phone jacks available - and TEST for a dial tone?