Could it be the yeast byproduct? Best way I've been able to tell what is on the bottom is by opening one up after a week or two. Make sure it's carbonated. Taste test (drink and enjoy). Lastly, make sure that the last drink is what you think it is - sugar.
If it is all sugar and not the yeast byproduct, try shaking them all up and turning them upside down, in a case (for support), for a day or two then do it again leaving it upright. There shouldn't be a lot of oxygen in the bottle. So there won't be any concern over oxygenating. The technique I described is essentially increasing the surface area for contact between yeast and sugar.
There are a lot of reasons why the yeast might not have taken hold in your brew... Pitching too hot. Didn't give the yeast enough time at optimal temp for pre-pitching multiplying. The yeast may not have received their initial gulp of air or provided enough trace nutrients before going down to ferment. Etc.
Additionally, with lager yeasts you will want to pitch cooler. Pitch a lager yeast when below 70 degrees F. Cool very slowly (days), let the yeast open up. Too fast can cause the yeast to stay dormant (don't just stick in a refrigerator), but also know that lager yeasts are slower fermenters and optimally grow when in the range of 40-60 degrees F depending on the strain. It's good brewing form to know your yeast before dumping it in the primary.
Here are some good reads:
Good luck and Cheers!