I have seen many posts on the forum from people saying that their listings are not showing. I thought I had this problem also until I saw that the Best Value filter was on by default. I think that many buyers do not know that the Best Value filter is on by default so they are not aware that they are not seeing all of the listings. If you are not seeing your listing check to see if the Best Value filter is on.
I have sent a message to @TeamStubHub to ask if the Best Value Filter can be changed from a default option to a buyer/seller filter that must be turned on just like all other filters must be turned on by the buyer/seller. I received a quick reply that this is a known issue that is being worked on.