Literary folly

The book I'm currently reading is due at the library today. I went online to renew the book as I've done in the past with others. After I clicked 'Renew', a message next to the book says 'ON HOLD' and would not let me renew. What the hell? 'ON HOLD'? I then proceed to search for the same book in neighboring libraries that are part of the same network of libraries and found there are several copies that are on the shelf. So, you mean that the other copies could not be used for the hold request?

Well, my plan now is after work, check out another copy of the book at another library and return the one I have. Reading is fun-da-mental.