Culturing yeast from bottles is a hit or miss. In this case, it seems like a miss. Toss it and start with a fresher 6 packs.
After some time, mostly anything will start fermenting unless it is 100% sterile, which is rarely the case.
The amount of viable yeast in a bottle can be quite low. Pitch in a very very small amount of wort, the dregs of 1 bottle into 30 ml or even less, then step it up 10 folds to 300 ml 24 hours after first sign of fermentation. Test to ensure your 300 ml attenuated at least 75% and that there is no off-flavors.
If anything seems odd, don't use it. It is just not worth it.