I'll concur too using potassium metabisulfite.
Make you use spring water or water that has been filtered through reverse osmosis. If you are using softened well water, there is dissolved salt there too.
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It's not that unheard of to get buckets nearly or fully fermented.
The way I avoid such episodes is to pick up pails right after the brew store received their shipment. It is a pain to keep calling them, but it's one way to ensure you are getting it as fresh as possible.
One thing no one has mentioned is TA (titratable acid). Blueberries are high in acid. That and what alcohol has fermented thus far is killing your yeast.
Take a cup of your wine, cut it with 1/2 cup of warm water. Pitch EC-1118 yeast in that and see if that will get going. Once this "starter"...
I know someone that makes sulfite free red wines. They need to be consumed before the one year mark. After that they oxidize and head downhill quickly.
It's way to early to judge it. Let it clear with time. Rack as often as sediment builds up on the bottom.
Don't taste until the spring. You'll be surprised!