If your wash hasn’t reached the advised specific gravity reading of 990 (just above the 1000) there are a few things that can cause this. In summer it’s almost always caused by over heating in the first few days of fermentation.
DO NOT THROW IT OUT.
The combination of yeast, water, sugar and hot weather can easily cause you wash to jump 8-10 degrees higher than the ambient temperature. This quickly kill some of the yeast and the remaining yeast won’t be enough to work with the quantity of sugar that is remaining unfermented. If after 5-7 days your wash hasn’t reached the desired temp in summer I’d suggest you give it a good stir and wait another 2-3 days. If theres still no change you can still go ahead and distill it. Your end result will be determined by exactly how hot it got in those first few days. You will definitely get something for your effort.
In winter you can still appear to get a similar result but this easily fixed. All you need to do is warm your wash up. A heater pad is the best for this. They are a worthwhile investment. Even if your wash has been down for 2-3 weeks in winter you can still put a heater pad under it and warm it up and finish it off.
The ideal fermentation temp is 24-28 degrees.Anything less than this and your yeast could be sleeping and can be woken by warming it up. Of course, as I’ve explained above theres no way of saving it if it over heats.
There’s more information in the question about yeast and temperature.