As the red error message at the bottom of your screenshot says (and your DNS records clearly confirm this), you have an existing A record for the same root domain pointed to an AWS IP address.
If this were to be permitted, where would requests be sent to? AWS or Searchie?
You need to decide which service gets the root domain… and use a subdomain for the other. And if you’re not using the AWS service any longer, just delete the A record so you can add the CNAME record.