Well, you should check if it's a highland lowland or ultrahighland nepenthes.
Lowlands need very hot and humid conditions with no temp drop
Highlands, can't have their temps in the 90s and many rewuire a drop to the 60s at night. i have found that most of my highlanders de well on my windowsill and pitcher well to (ventrata, ventricosa, alata, maxima, ephipppiata, burbidgeae, sanguinea)
The absence of pitcher fluid can be caused by underwatering, low humidity, or too extreeme temps.
Nepenthes can be overwatered though, never keep them in standing water, no matter what people say. Keep the soil damp, to a bit wet.
Hope that helped.