ISBNsearch.org, like many other online ISBN databases, relies on receiving, processing, and updating data from various sources, which may include publishers, distributors, libraries, and more. This process takes time, and there’s often a delay between when a new ISBN is assigned and when it appears in these databases.
The book associated with the new ISBN may not yet be released, or the metadata associated with that ISBN may not yet have been fully distributed or updated across all platforms. Also, if the book is self-published or released by a smaller publisher, there may be additional delays in data distribution.
Furthermore, each database may update its records at different intervals - some might update their databases daily, others weekly or monthly. Therefore, if a new ISBN is assigned, it might not immediately appear in the ISBNsearch.org database. If a newly assigned ISBN doesn’t appear in the search results, it’s usually a good idea to wait for a few days or even weeks and then try again.