You have a custom domain setup for your Wild Apricot account - and it is now setup as your primary domain (= used in emails etc.). It looks like your domain settings were changed/reset and your domain no longer points to Wild Apricot server. You need to fix this via your domain registrar. These instructions might help: Custom domain setup

If you think it will take you a while to fix that, we can change the settings on your domain to use your free Wild Apricot domain as the primary one - until you fix the issue with the custom domain and let us know. Please confirm if we should do this.