In order to add a resource to a group reservation, we will need to add this directly on the reservation record. Resources associated with Program Record are not automatically added to the reservation. 

Connecting resources to a program event will only "reserve" those resources when a particular program event is set up. So, if the sole purpose of attaching a resource to a program is to display on a group sales reservation, than remember to disconnect it from the program and connect it only through reservation otherwise you may get a conflict alert when you try to connect the resource to a group sales reservation with the program event already scheduled.

If you would like to see resources added to reservations based on the resources associated with the program, we have an idea on our Community regarding this: