Don't know the why of the communication issue and I would consider that a serious issue if it goes on for a week or more despite repeated attempts because it may indicate something has happened to the owner.
As to your belief that the cancellation would be done in plenty of time to rent it again or get points back, you may well be incorrect on that one. If he cancels, he will get the points back, but if that occurs at anytime during the last four months of the owner's use year or the owner used banked or borrowed points, the points cannot be banked into the next use year and must be used by the end of the current use year, which may be impossible even if the owner could find another renter, because all available rooms for which the points can be use may be booked, something that often occurs when you are four months or less out from a desired arrival date. In that situation, the only possible way the owner could break even and not lose the use of any points is to find another renter who wants to stay in the same type of room at the same resort for exactly the same time period that you currently have, and thus the owner could attempt to just change names on the reservation, and that is not something that is easy to do.
As to being able to cancel and get money back, that is really an issue between you and the owner. If nothing was said when the reservation was made about getting money back if you cancelled, then your legal entitlement to a refund would depend upon whether it was customary for
DVC rentals that owners make such refunds if you cancel, so that you could claim that custom is implied as part of the agreement. However, with
DVC rentals, the custom is actually the reverse in that DVC owners most often insist on no refund if you cancel.
