We made the beer, it fermented fine, then waited to bottle (maybe too long afterwards) added sugar and bottled. After waiting for the required time opened a bottle only to find it flat. Can we add more yeast and still save this batch of beer or do we need to start over...? Can the original brew be salvaged?
I don't think this question can be answered without more information:
- what was the final gravity?
- how much priming sugar did you add?
- what was 'the required time'?
Probably the best advice is wait another week or two and then sample it again. I often find it can take several weeks after bottling for appropriate carbonation.
For best results, you should add priming sugar to a bottling bucket rather than to each bottle. Dissolve your sugar in hot water, then rack on top of it. Gently stir the beer for a few seconds to mix it. DO NOT AERATE.
A good rule of thumb for carbonating in bottles is to let them sit at 70-75F for 3 weeks.