This article describes the case when trying to register to FortiGate to FortiCare through FortiGate GUI, the user needs to select the correct reseller from the dropdown menu. However, sometimes this option keeps on spinning and does not show the correct options at all.
Scope
FortiGate, FortiOS.
Solution
One of the main reasons for this issue is connectivity to the internet. Make sure that FortiGate can reach the internet by pinging using the IP address.
It is also important that FortiGate should be able to resolve the hostnames using the system DNS configured on the FortiGate.
Make sure that the DNS servers used on FortiGate should support the correct protocol (cleartext or DoT or DoH) as per the following KB article: Technical Tip: Changing the DNS protocol used by FortiGate to initiate DNS requests.
The wrong DNS protocol configuration will result in unresolved hostnames and FortiGate will not be able to reach the internet using hostnames/URLs.