it sounds as if all you tried so far was to add the FortiGate from FortiManager.
If you haven't already, you can try the other way around, point FortiGate to FortiManager. On FortiManager you should usually see an unauthorized device crop up in root ADOM, which you can then authorize and add to an ADOM. To do this, simply configure central management on FortiGate; how this can be done varies by firmware, but via is CLI is fairly straightforward: https://docs.fortinet.com/document/fortigate/6.0.0/cli-reference/680692/system-central-management - set the mode (normal) - set type (fortimanager) - set fmg (FortiManager IP or hostname) - set serial (FortiManager S/N) - set enc-algorithm (default or high)
+++ Divide by Cucumber Error. Please Reinstall Universe and Reboot +++
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