What is the difference between Reject and Block for a vendor?

Both stop the vendor from signing in. The difference is what they mean and what the seller sees.

• Reject marks the vendor as Rejected. Use it for an application you don't accept. At login, the seller sees "Your seller account is not active yet."
• Block marks the vendor as Blocked. Use it for an existing seller you want to shut out. At login, they see "Your seller account is blocked."

Both are on Vendors → Manage Vendors. Neither one deletes anything. If you change your mind, click Approve to make the vendor Active again.