First of all, great question!
If you haven't already, setup your John Deere / Agworld integration. By setting this up, you should then have access to use the "Send Controller File to John Deere" options throughout Agworld.
The equipment options you see in Agworld when sending a controller file should stay in sync with the equipment you have setup in JD Link. If you do not see a piece of equipment showing up, contact your John Deere Dealer that you purchased the equipment from. (The JD Dealer possibly needs to assign that piece of equipment to your JD Link account. Once the equipment is assigned and activated in your JD link account, the equipment should show in your JD Operations Center.)
Your equipment must also have an active John Deere Wireless Data Transfer (WDT) license on it for it to show up as a machine that is available to send controller files to in Agworld. If you do not have an active WDT license, the equipment will still show up in the JD Operations Center, but you wont be able to do any remote file sending to that equipment from Agworld or the JD Operations Center.
Otherwise, Agworld should stay in sync with the equipment list that has been setup in your JD Operations Center. If for some reason you see a machine in the Operations Center but not in Agworld, try refreshing the connection as you are Sending a Controller File to John Deere within Agworld.
If you are still experiencing issues, reach out to Agworld Support.