I would remove the V1 then reinstall it. Sometimes it might not be seated completely and therefore not making contact. Other times it is the pins not making contact with the sockets. This process will at least let you know if it is the connection at the tube. If you get any connection then you may consider cleaning your sockets or taking your amp in for a cleaning. If you decide to clean it yourself get some Deoxit, unplug your amp, and apply it to the pins of the culprit tube. Then work the tube in and out (like sex, if you know anything about that). Give your amp a little time to dry then reinsert the tube and see if you get a better result. The contacts that the pins and socket make sometimes get dirty after time and you end up with not so reliable performance. This is most evident in the case of a tube manipulation whether it be a swap, a check, or just a straight up replacement. Some say that the Deoxit makes for a better sounding result. I myself just think that the cleaner contacts just allow the signals to flow easier thus giving you a truer result. Afterall, parts sound like they do and regardless of what you do you will only get a truer assessment if the contacts are clean.
