It sounds like the Owners Corp was either wrong before or they are wrong now. But there’s a difference between what’s fair and unfair and what’s right and wrong. The only way you can establish which applies is to establish which bits of this are common property and which aren’t (and that means looking at the original strata plan).
However, I’m betting an external wall IS common property, in which case it doesn’t matter if it was wear and tear, damage by vandals, a missile attack from disgruntled neighbours or an act of God. The only circumstances under which an individual owner would have to pay for the repair of common property would be if they damaged it themselves. You clearly didn’t and if the previous owner did, then the Owners Corp’s beef is with them – but they still have to pay for the repairs.
This sounds suspiciously like the EC has put a claim in to their insurers and they’ve been told it’s wear and tear, therefore not insured. That may be so but it changes nothing – the Owners Corp has an absolute responsibility to maintain and repair common property. It’s not your problem if they can’t get their insurance to pay for it.
However, if by some quirk the previous owner had been given permission to erect the sun-shade and there was an exclusive use by-law to that effect, then the chances are that the damage may well be yours to repair. But if that is the case it will be in the by-laws. If it’s not in the by-laws, then it’s more than likely an Owners Corp responsibility.