[wildfyr]

Were your molecular sieves activated properly? Fresh from a supplier they are often not well activated. They require considerable heating (>250°C), usually under vacuum to activate, and can become deactivated even if stored near 100°C! They should be kept in a sealed desiccator after activation.

Activated sieves can be discerned by putting a few in your gloved palm then adding a drop of water. The sieves should become almost too hot to hold.