Keywords: requests, status, available copies
When requesting items, you may see several copies in the holdings statement and some may even have an "available" status, but you get the above statement anyway. Why isn't the patron allowed to request the item or a place a hold?
First, keep in mind that the only items that are requestable are items with an 'Available' status -- has the '-' (dash) status code. But even if it does have an available status, there is still one more check before the system can let an item be requested. It checks the item type. All items contributed to the central site are mapped to a central site itype which determines its lending status. Only itypes 200, 208, 209, and 212 are requestable. Itype 213 is only requestable by a patron from a CRL Member institution (see here). All other itypes are not requestable even if their status is available.
If all items are checked out, you should be able to place a hold on an item as long as there is at least one item that can have a hold placed on it (it is requestable, and does not already have a hold on it).