If you haven’t already done so, I would send a formal letter asking them to send you details of when the work was likely to commence. If they say it isn’t, or just don’t reply within two months, then you could pursue them under Section 232 (2) of the Act for failure to fulfill a function as the committee of the OC.
Or you could just send a letter saying that, given their failure to complete the job for the whole building, you have several options, any or all of which you might pursue.
1. Seek orders at NCAT under section 232 (2)
2. Seek the compulsory appointment of a strata manager to take over the running of the block
3. Seek resitution at a civil court for “fraud against a minority” which is where a majority of owners (or shareholders etc) makes a decision that benefits only them to the detriment of the minority of owners.
4. Seek removal of committee members (at NCAT) for failure to fulfill their statutory duty to run the building for the benefit of all owners.
And if any or all of the above tactics appeal, you might want to consult an experienced strata lawyer who will write a letter for you that might get them moving.