Hello @Hazel54,
I'm not sure if this what you've done. When Airbnb suggested that you request a cancellation and wait 48 hours they meant the following. You must press the cancel button and then select the reason "My host needs to cancel".
To do this go to your trips and select your trip. Then click on "Change or cancel". Then click on "Next" in the "Cancel" box. Then click to select the reason "My host needs to cancel" and click on "Continue" to complete the process. Then if the host accepts or ignores the request the trip will be cancelled and you'll get a full refund. If the host declines the request the trip stays as is.
Steve.