You can delegate those powers to the strata manager. Otherwise, this is what the Act says.
Part 3, Section 19: What happens if chairperson, secretary and treasurer are not appointed?
(1) An Adjudicator may, on application, make an order appointing a person nominated by the applicant (and who has consented to that nomination) to convene a meeting of the executive committee of the owners corporation if there is not a chairperson, secretary and treasurer of the executive committee of the owners corporation after the first meeting of the executive committee has been held.
(2) The meeting is to be convened and held within such time as is specified in the order.
(3) A meeting held under this section is taken to have been held by the executive committee of the owners corporation.
(4) An order made under this section may include such ancillary or consequential provisions as the Adjudicator thinks fit.
(5) If an order made under this section so provides, notice of the meeting may be given in the manner specified in the order.
(6) An application under this section may be made only by an owner, mortgagee or covenant chargee of a lot in the relevant strata scheme.
What does that mean? I have no idea … but in most cases if nobody wants to be an office-bearer, then it gets delegated to the strata manager. If you don't have a strata manager, then you trundle along in anarchic fashion until something goes wrong and/or someone complains.