Can't block NGROK proxy app

Bonjour,

On a Fortigate 600D, v6.0.2 with the last application signature DB I can't achieve blocking outgoing NGROK tunnels.

Changing the behaviour to block make the connection longer to establish, but connection happens. Looking at the trace after a few blocking NGROK sessions, I get authorized HTTPS sessions ...

Anything more to do in configuration to block NGROK ?

Thanks