My Ebay bid was rejected?

I've bid bidding and buying items on Ebay for about 1 year now. I tried to do the feedback each time and I have a paypal account. I emailed the seller a question about what shade the makeup was and they answered me. Then I went to bid and my bid was rejected. I have a paypal account etc and no violations. I can't imagine why they rejected my bid. I did notice though that most of the bids were identifed as private bidders - maybe that means something?