The usual thing to do would be to claim on your own insurance.
You could try making a formal damages claim against the OC. To be successful you’d have to establish that the OC itself was in some way responsible for the theft or at least partly responsible. That’s not an easy thing to do when the area of the theft is a common one that has to accessible to all occupiers. Security in those areas is always going to be limited. I have seen a couple of successful cases however where the OC was aware that security had been compromised but failed to remedy the situation in a reasonable way/time-frame.
I’d agree that the strata must maintain the CCTV. But that doesn’t mean it is guaranteed to be functioning 100% of the time. Unsupervised CCTV systems are common in stratas and are designed to run automatically with minimal supervision and maintenance requirements. If the OC had known for some time that its CCTV was faulty but failed to get it repaired, it might be different. The OC is claiming however that it was a “glitch”.
You are correct that a Tier 1 OC in VIC must have a manager. But that’s a Strata Manager not a Building Manager. Building Managers are not part of the strata legislation.