• this is busted with at least ascents in my branch
• it is not specific to PVG code, the classic ascent guidance similarly is not working
• it is not, as far as i can see, anything to do with the Ascent modules themselves, or the GuidanceController.
• inside the ThrustController on every tick, even when modules are enabled the s.mainThrottle that comes in via the args to Drive() is set to zero. the ThrustController sets it to 1.0 at the end, but the next tick it is back to zero. when the ThrustController is disabled it goes back to zero. nothing is calling ThrustOff in the ThrustController, nothing seems to be directly poking the throttle that I can see.
• maybe "Default Throttle in Prelaunch" being set to zero in KSPs main options itself is screwing things up? (nope, setting to 100% doesn't help)

seem if you manually throttle up to 100% first before launching then this works, so somehow we're remembering the last manual throttle setting and reverting to that.

(at least that is what has been reported to me)