It's frustrating for sure, and I have a couple tubes the same way. For sure the tube by itself will not show pressure on your guage, as it probably has less than a pound of pressure.
I would NOT use anything on the core to tube connection. Any cement or paste will allow the rubber to slip out of place much easier than if it's assembled dry. Many years ago I learned that the hard way on the rear rubber gasket of a Chevy V8 intake manifold. After 3 tries, an old timer in the shop wised me up.
