Don't guess. Read the terms of the United Explorer offer: This product is available to you if you do not have this card and have not received a new Cardmember bonus for this card in the past 24 months

1. You already meet the first criterion, because you do not have the United Explorer Card. The card you do have is irrelevant.

2. If you previously held the United Explorer the clock started running when you received the new account bonus. If 24 months have elapsed, you are eligible now.