Two possibilities. 1., sellers can block bidders by user name- usually a past dispute that did not resolve well. 2. Private or qualified sale. Bidders have to contyact seller and exchange added info- then the seller puts you on the list of bidders OK to bid. Typically high dollar items- cars, high end collectables etc. Sometimes seller requires certain amount of feedback for bidder to be sure they are an actual paying adult.
Or a stray electron took a wrong turn in Albuquerque, NM and the message was in error
