You can only make three best offers, but can still bid for the item, or use the buy now option, if there is one.
If the seller has blocked you from bidding, there's nothing you can do. EBay now includes a best offer option by default in every listing. Many sellers don't like or want this. Perhaps it's the seller who feels annoyed if you made what they feel were insultingly low offers.
If this what's happened, it's their right to block you. They don't have to justify their reasons. You may just need to move on and look elsewhere.
