We would recommend that the TP worker firstly try to get things moving, if possible, by addressing members of the group. Try to establish if there is a problem or not and also to mention that by not meeting they are in all probability, not strictly adhering to the terms of the groups constitution.
This is obviously dependent on the constitution itself, but if the group has been 'recognised' there should be something alluding to a scenario similar as this. The next step should be to call a meeting of the said group's quorum (preferably giving 28 days notice). You should now establish through this meeting whether the group wants to continue functioning or not. If the group members present agree that they want this to happen, they can opt to elect a new committee.
If this is not the case the group should organise a further and formal 'Winding Up' meeting (again, giving 28 days notice). If in the worst case scenario there is actually no quorum, then the group will probably have to be 'wound up' there and then and that all relevant books, accounts etc are forwarded on to the party specified in the original agreed constitution.