After you have added a custom domain to Systeme io, you will need to assign or connect this domain to your funnels before it is ready to use.
Domain Assign in Sales Funnel
In the sales funnel, click on the Settings (top-right)
Under Funnel domain, drop down the selection and select the domain you have just added. Remember to save the changes.
Domain Assign in Blog
In the blog listing page, click on the Settings
In the Blog domain, drop down the selection and choose the domain you’ve just added. Save the changes.