Okay, okay, no panic, it's all under control!
Yesterday I installed the new Mac OS X High Sierra (clean installation, I prefer!) And one of the first things I do since 2011 is installing my favorite FF400 drivers.
Unfortunately it didn't work: red light on the display, no apps on the dock. :-(

So I began to check, reinstall, make voodoo rites and ritual dances ... nothing to do.

Looking for "something" on the forum I found this very useful post where, in fact, it is said that the Gatekeeper of the system doesn't advise with the pop-up as it usually does for other applications.
So, I did nothing but open the Terminal and write:

sudo spctl --master-disable

to disable completely the Gatekeeper and immediately the red light went off and the apps were loaded, placing the two icons on the dock.
For every good measure I restarted the system and now I have my wonderful sound card running again.

I'm obliged to warn that by disabling Gatekeeper there is a risk of installing unwanted programs, so I'm not taking any responsibility for the action I have mentioned.

To check the status of the Gatekeeper enter the command from the terminal:

spctl --status

To re-enable the Gatekeeper, just enter the command (always from Terminal):

sudo spctl --master-enable

I haven't yet checked if reactivating the Gatekeeperthe problem back again, I will do it on weekends, after installing the other programs I need.

Have a nice day and good music with RME.