"Failed to save changes" error message when trying to add New Application Signature

Good Afternoon,

I've been trying to add a new application signature for the last day with no luck! Everytime I add  F-SBID (--name "electra.connection"; --protocol tcp; --service HTTP; --dst_port 5817; )

our Fortigate E61 just returns an error saying "Failed to save changes" and nothing else.

Our Application Control's Unknown Applications category is blocking [Active] is blocking a certain app. I don't want to enable that entire category just for the sake of this one application. I want to create the above application signature, and set it as an application signature override in the Application Control options.

Kindly advise if I'm going the wrong way about this or if you've encountered the same problem somewhere and how to fix it.

Thanks