did you check, whether the 'WHEN' condition is true at all ?
Not that you scheduled from tomorrow and expect it to work from today?
Also, AFAIK, out-of-office has to be enabled on the server version of your mailbox and not on a local replica.
I suppose as a normal user it is not possible to check the schedule for the OOO agent on the server ... for me the server is outsorced and I'd have to call somebody
Juliane