Boosting a Lithium Coin Cell
Schottky diodes don't make great blocking diodes for the purpose of power rails. They have often have high reverse leakage currents.
Your initial in-rush current is probably high causing the battery voltage to dip below the part's UVLO. To verify this put a scope on your battery and set it to trigger on it dipping more than 100mV below it's nominal value. Make sure you are looking at things at micro-second resolution (like 10 us/div). Post your results here.


Also, if your current requirements are low (&lt;150mA) you can get away w/ a charge-pump.