Although you are trying to be helpful for the guest, @Kelly284, it might be better for the guest to follow up with Air BNB. There may be issues with the credit card used by the guest for the credit to be posted. Just give them contact information for Air BNB if they do not have the phone number usually found on their reservation confirmation.
As to your cancellation, I hope you involved Air BNB in the process so you will not suffer the host penalties. If it was an IB reservation you can cancel if you are uncomfortable with the guest. If not, you may have reasons for cancelling that are acceptable but require human intervention.