Please don't post things that will alarm beginners. I disagree with you. It is the CO2 that keeps the scoby afloat. If the CO2 can escape, or it is at the end of the fermentation, the scoby may well sink and still be a perfectly viable scoby.
A 'dead' scoby may well sink, but not all scobys that sink are dead. remember a scoby is not a single organism, but is mad up of billions of organisms.
*Made
And I never said that the scoby is dead, I said chances are it MIGHT BE if it sinks and can't build back up after an extended period of time. I also said *which you didn't quote* it takes time for it to float back up and build up Co2- which again I said "it needs to get used to its environment".
It's more then just C02 that can make a scoby sink
One of the causes could be reduced yeast activity
Could be poor c02 buildup
Could be temperature of ferment
Yeasts tend to be more vigorous in warm brews-
I agree it might not be dead but a muted state is NOT fermenting , it simply can't.
Why not start another brew?
Didn't see you come up with a solution rather then just point out what you thought was wrong.
Source: Grown a 1000 + Scobies &
http://kombuchahome.com/what-to-do-if-my-scoby-sinks/