I'm a beginner bread maker and have had great success with Bittman's no-knead bread recipe. My friend gave me some sourdough starter, it had been in her fridge for about a month with no feedings. I gave it some flour and filtered water last night and waited 12 hours. Nothing really happened, there were a modest amount of tiny bubbles. It smells like sourdough and doesn't have any weird colours or anything. I went ahead with the rest of the recipe (and saved 1/4 cup of starter for the next batch) but the dough hasn't risen at all after 6 hours. Is the starter dead or should I try using the starter again?