990 uGC - PPU Column - Negative Peak (He Carrier)

I have a brand new 990 microGC with two columns - MS5A (20m with 3m BF), and a PPU (10m + 1m BF). I am trying to develop a method, however, am running into the following problem. 

The gas mix being injected - 500 ppm CH4, 500 ppm N2, Balance H2. My PPU column is showing a very large negative peak right off the bat. I am not sure what is going on. The method I followed was similar to what was used in a documented in the Agilent website for Hot Spring Gas Analysis. The carrier gas for PPU is He. Any help is appreciated.

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