Firstly have you checked your hydrometer is reading correctly ?
To check draw some tap water(ideally distilled water should be used) at 20C into your trial jar and float the hydrometer in it, it should read 1.000 :thumb:
You'd be surprised how many hydrometers are wrong :shock:
Also has the fermentation been conducted at a constant temperature, ideally 18 to 20C? Yeast behave themselves best when given constant temperatures.
If your hydrometer is correct and the temperature was OK, try gently stirring the yeast sediment back into suspension with a sterilised long handled spoon, taking care not to splash the cider too much, this may restart fermentation.
If it doesn't then my advice would be to either bottle in PET bottles or if using glass, use no more than 1/4 tsp of priming sugar per 500ml bottle as with a gravity of 1.004 there is still quite a lot of potentially fermentable sugar in solution and the risk of exploding glass bottles is a very real one :shock: