I did some testing and it seems item effects that can proc when attacking do not work with ranged even when they should according to the item description.
I equipped my repeater mechanic with Fabricator's Bracers and Parasitic Breastplate with Paranoia. Both Cannith Combat Infusion and Paranoia descriptions state that they work with ranged or melee attacks, but no matter how I tried they didn't proc at all when shooting with a repeater. When I switched to melee they worked normally, it didn't take very long for them both to proc.
Also Greater Vulkoor's Cunning set bonus does not work with ranged attacks, nothing happens on a roll of 20. But that does not specifically mention that it should work with ranged, so I don't know if it's WAI or not.