Preview Monitor / Mercury Transmit no longer working?

[VFXbear]

Since the update to 17.5, I'm no longer seeing a preview on my 2nd monitor (connected via HDMI).
Turning the Mercury Transmit function on/off in preferences doesn't make any difference.
Pressing the usual "/" on keypad shortcut stopped functioning as well.

Anyone else experiencing this?

My config :

[Jose Panadero]

Have you tried to remove the After Effects Preferences? You can do it by pressing COMMAND+ALT+SHIFT as soon as you open After Effects. You will be prompted to delete the preferences file. Click OK and try to set up your video preview again to check if it works.