What are you connecting to, a traditional telephone wall socket or the back of the VM hub?
Do you get a dial tone if you plug an ordinary telephone into the same location?
There is not too much to go wrong connection-wise. The trueCall plugs into the phone socket, the phone plugs into the back of the trueCall unit. The trueCall needs to be powered. It should show a single green light on the front when ready and waiting for a call.
What sort of age approximately is the phone you are trying to connect?
Do you have a setting for 'pulse' and 'tone' dialling on your phone? If so it should be set to 'tone' dialling. Could be via a soft setting on the phone display setup or maybe a switch on the phone case. Newer phones may not have the option and may just be set to tone dialling already.
You could also see if you can borrow a different phone to try into the trueCall, with the phone set to tone dialling.
If that is no use, you would need to give trueCall a ring for advice. There is a free 0800 number
There have been a couple of topics in the past where users have had issues with the phone not ringing or caller ID not working due to the setup of individual VM phone lines. trueCall have been able to remotely dial in to the unit to change the trueCall setup to match the VM phone line.
Can't recall any past mentions of a no dial tone problem though.