How long did you let it sit? Did it sit in a fridge or in room temp?
I'm about to rack into TAD bottles for the first time myself, so I'm no expert. Instructions for forced carbonation say "fill bottle, attach valve, insert CO2 cartridge, put in refrigerator, wait about 7 days". Also it says that when force carbing it takes about 1 cartridge to carb and one to serve.
The Primaries: Apfelwein | Liquid Light IPA | Dark Star Stout
On tap[-a-draft]: Liquid Light (Aurora)
Aging: The Eleven [Barley Wine [normal+oak'd]] | In The Court of the Crimson King [Raspberry Apfelwein] | Lighthouse Girl [Orange Mead]
Planning: Wit, Porter, more apfelwein and mead.