A: No. eBay does not send any notification. The user will simply find that they can now interact with your listings.
eBay’s block bidder/buyer list is a powerful tool for sellers. It allows you to prevent specific users from bidding on your items, purchasing from you, or contacting you via eBay’s messaging system. However, circumstances change. A resolved dispute, a mistaken identity, or a second chance for a reliable buyer might lead you to want to unblock someone. how to unblock someone on ebay
https://www.ebay.com/cnt/blockedlist