My guess: Q+ is a marker for when Q Group/Q Representative is in the field, which would be supported by the mobile link to yt from before, and by this >>916499 anon's theory re: >Transfer communications to military grade devices.
tl;dr Q was operating in the field using hardened, but clearnet devices. A sniffer was launched and detected, so Q is forced to return to military-grade devices and, to keep the op safe, goes dark ("rigged for silent", used before).