[Koha] Check-in failed

I have checked out some books for testing purposes and now when I try to check them in I get a message that says Check-in failed under the Patron->Details->Checkout tab. What would cause this and where can I find more detailed information? Under Home->Administration-System preferences->Logs I have them all set to Log. Thanks, Paul Paul Dokken Software Developer SIL PNG Communication and Technology Services Ukarumpa EHP 444 | Papua New Guinea cts-prog3@sil.org.pg +675-537-3544 x4404 {Telecom} +675-7081-8666 {Digicel}