Is this message coming in the form of an email from ebay itself or a red text error that you're getting when you try to bid on or add to cart a large number of items from a single seller? Many sellers have blocks that prevent a single user from buying a large number of items at a time and the same goes for bidding. Additionally, this can be set to new users specifically for a variety of reasons.
With more information, we can provide better insight.
p.s. Don't click on any links in emails. If the message came from ebay, you'll find it somewhere in messages or the information conveyed elsewhere within what you see when you log in.
