I'm in SNH and having similar problems. I blame the dam trees for not producing lol. Seem to blame the trees every year but still holding on. I've got 115 in and all gravity I've collected around 100 gallons in 2 weeks now. I just bought a new evaporator this season and have fired it up once so I feel your pain. I'm hoping to go vacuum next year and solve the no sap problem.
2018 - ?? 2x5 lapierre raised flue evaporator
2017 - 150 taps mixed 2.5 x 4 evaporator
2016 - 230 taps taps mixed 2.5 x 4 evaporator
2015 - 115 taps mixed buckets, bags and, water jugs. 2.5 x 4 evaporator.
2014 - 55 taps mixed buckets, bags and, drop lines. 4 steam trays and a block arch. 3 gallons made tapped prematurely (lesson learned)