I wonder if it's related to a financing round. That's the usual reason for a quiet period. Not that we know Cytyodyn is in a quiet period, but if they are the reason could be because quiet periods precede the filing of a prospectus.

It would be unusual to make such a seemingly abrupt decision to initiate a significant financing within the span of two days, thus leading to the cancellation of the call, but maybe an opportunity arose. Anyway, just another guess.