On some SonicWall devices, when a configuration file is imported from a Gen 6 device, the SonicOS API isn't loaded. You'll see that the Zero Touch is enabled and connected, but it can't be managed successfully.
In this case, we need to SSH into the device and turn on the SonicOS API:
ssh admin@<ipaddress>
<password prompt goes here>
config
administration
sonicos-api
enable
commit
Very quickly you should see if pop up.
YAY!