Any communication between your Channel Manager and a sales channel can be found by going to the Channel Mapping tab for that sales channel and selecting the View Log button at the bottom of the screen.
iBex will display all previous updates including availability updates, bookings, amendments and cancellations, and any error's that may have occurred with the connection.
You can filter what is displayed by text (such as a sales channel booking reference number) and by date range enabling you to view what updates were sent and when they were sent or received.
Below is an example of the log for Booking.com (with the property name erased) where you can see a booking was received at 13:14 and 07 seconds (in the second log).
Booking.com were then updated with the new availability for the room type that was booked (which has the iBex room ID of 19860) at 13:14 and 45 seconds.
As you can see in the log below for Wotif, they were also updated with the new availability at 13:14 and 07 seconds.