There are three options available to you:
Your entry will be carried over automatically to 2021 at no additional cost. You don't need to do anything.
You may request
a full refund
Howler will be managing the refund process. In order to Refund your entry fee, you need to have a Howler Account with the same email address you entered the race with. Refunds will be done on or before 31 October 2020