Why am I unable to verify the domain in the landing page (404 error)?
The domain could not be verified from Zoho Marketing Automation, as it needs to be verified through Zoho LandingPage (They provide steps to verify).
First, You Need to check the details from the Landing-page :
1. The role must be checked — only the Portal Owner is authorized to add and verify the domain.
2. The CNAME entry must be verified and correctly configured.