I have tried everything I can, but I just can't seem to get a non-flavored kombucha to fizz. I have a green + black tea kombucha for F1, I have tried transferring it to a flip top bottle with no sugar, with some sugar, with a lot of sugar, even left it for almost 7 days in F2 after a 14 day F1, and no matter what, I get no carbonation at all, just a more vinegary taste. Any tips?