The primary A DNS record in Nexcess InterWox-CP is uneditable for an unknown reason:
You can change the primary A DNS record via the Nexcess support only.
It seems that trackspecmotorsports.com is the main siteworx account where we do not provide privileges to edit DNS records.
Go to my.nexcess.net and use the chat control in the bottom-right corner.
You can also creter a ticket, but tickets are responded slowly, and via the chat you can change the primary A DNS record fast.