It's a good question and I don't have an answer, but I have a wild guess. If no activity is outwardly visible and you have ruled out things like a leaky seal or other typical issue, it could be that the slurry was so old that the Saccaromyces is just not going to make it. The Brett and Pedro part of the lure will eventually get going, I am sure. You could add some new yeast to see if that is the issue. I also have concerns about the balance of the percentages on a re-pitch - I think it is possible that the saccaromyces that are alive may be woefully outnumbered and having trouble getting going. That is my WAG of the day...