Fredm, ... The OP's problem is that he did not force the payment of the delinquent MF through the closing escrow and follow it up with escrow instructions which would force the seller to give the delinquent MF to the closer and the closer to pay the delinquent MF.
If the buyer agrees to let the seller pay the delinquent MF and it is not paid, the buyer has no recourse against either the closing agent (it violated no instruction) or the broker (the broker didn't promise to pay the MF). The resort is not a party to the transfer, wasn't asked, doesn't care and will (rightly) deny use until the delinquent MF is paid.
The seller is someone probably unknown to the buyer and is hard to track down.
And, that's exactly why escrows are used for closing real estate transactions. The OP, by stating that he could have called the resort, demonstrates he still doesn't get it.
On eBay people think they are dealing with the actual owner of the timeshare. They aren't. They are dealng with an advertiser/selling agent of the true owner and a closing firm both of whom may or may not be licensed and bonded and both of whom may or may not be honest or competent. So, sometimes things go awry and the advertiser/selling agent and the closing company are insulated from liability to the buyer. ... eom