This is a sad situation, and I would hope your condo board would be more accommodating, given what’s going on in the world. BUT, there is no legal requirement that they do so. If you fall behind, they can take you to court, with the potential ultimate remedy of eviction. But that is a long process — and hopefully you will be able to catch up before then.
I suggest that you attend the next board meeting, asking in advance for a slot on the agenda to plead your case. Then they will have to publicly document their actions– since under law all condo meetings must be open to the owners.
Perhaps you could ask a neighbor and fellow-owner to speak in your support. Hope that works, and hope you’re back at work soon. And you may ask other neighbors to protest the special assessment at this point. Surely, it can’t be easy on anyone these days.