I did my first homebrew a fortnight ago, an american IPA BIAB-style on the stovetop. I ended up with a low OG (~1.045 - target was 1.075) and now after two weeks of fermentation a high FG too (~1.026). I have tried readded some dry yeast but a day later the gravity has not changed.
After a little reading it looks like one of two things went wrong: I forgot to shake the carboy to aerate it & maybe I mashed at the wrong temperature - I heated to strike temp OK but then just left the pot (covered) for an hour without any insulation & without checking the temp. Apparently if you mash too low then you can convert the wrong kind of sugar for the yeast, which is ringing true here.
Is there a quick way to check if the beer is full of unfermentable sugars?
As an aside, would you even bother to bottle such a low-ABV high-sugar beer if that is indeed what has happened? It smells like beer mixed with syrup..