Will not dial out on landline in the tone mode but

There's something wrong with the base unit that connects to the phone line. It's not sending any audio to the phone line, which would explain why tone dialing doesn't work and people can't hear you. (Pulse dialing doesn't need the audio tones so it will still work.)

I've never run across one doing this before. The problem is almost certainly some electronic failure, and I doubt there's anything you can do other than replacing the thing. If this is still under any warranty it should be up to the manufacturer to repair or replace it. If you got this from VoIP service provider, contact their customer service department.