What's happening
If a reservation booked to your Opera group block is showing a $0 rate, it almost always means that the room type the guest was booked into does not have a rate assigned in Event Temple.
Opera requires a rate to be set for every room type in the block — even room types you don't expect to be used. If a room type is left without a rate and a guest is booked into it, the rate will default to $0 automatically.
How to fix it
In Event Temple, open the affected Booking
Go to the Room Block, click show empty rooms
Review each room type listed. Any room type showing a blank or $0 rate needs a rate assigned
Click Edit Rooms and Rates, assign rates
Click Save
How to prevent this
When setting up a new group block, make sure a rate is entered for every room type added to the grid — including secondary room types like junior suites or accessible rooms.