Error mount - error calling mount

[shaman21 65]

Hello someone could help me solve this error ... When I click the mount it does not appear.

sysser:  SYSERR: Oct 27 17:36:15.456929 :: Summon: unkown mount [itemVnum 50052, mobVnum 20104, mobType 1 (need 9), owner 10090 LastOrder]

She is called the seal goes to the slot below the character but the mount does not appear, this is happening to all even the military horse.