Technical Tip: Category 'Operational Technology' is not available in category list of application control profile

FortiGate has a valid license for 'Operational Technology (OT) Security Service', and can connect to the FortiGuard servers and download the relevant signature databases, but the category 'Operational Technology' is not available yet in the application control profile, while exclude-signatures is set to 'ot' in the IPS global setting as well as below:

config ips global
    set exclude-signatures ot   <------- 
end

To resolve this issue, enable an application profile on a firewall policy and then run the commands below via CLI to get an update from the FortiGuard server:

diagnose debug disable
diagnose debug reset
diagnose debug console timestamp enable
diagnose debug application update -1
diagnose debug enable
execute update-now

After a couple of minutes, disable debugging by running the commands below and then check the application profile; the category 'Operational Technology' will be available:

diagnose debug disable
diagnose debug reset

The following article can be referred to configure Application Control via CLI:

Technical Tip: How to configure an application sensor via CLI