OWA calendar resource

enviroment: NT4 SP6 Exchange5.5 SP3
The problem is when user try to book a room the user will not get room confirmations when booking rooms in outlook/calendar.
it seems that nothing gets books even though it says it is.

calendar resource requesting are not coming back to user with any kind of
response, approved or denied.
This just started to happen 2 weeks ago
Does anyone have any idea what could be the problem
Thanks