Assuming you are keeping it sufficiently watered, that strawberry plant has a serious problem, to the point where I suspect it won't survive.
Too much water seems the most likely reason. That pot it's in does have a hole in the bottom, right? Too much water causes the roots to rot, and the plant to die.
Another possibility is vine weevil larvae. They're little white grubs, about 1cm long, which eat roots. Plants in pots are especially prone, and strawberries are often targeted. However, since you plant is indoors it seems unlikely that the adult vine weevil could have gotten in there to lay its eggs in the first place.
Either way, I would recommend turn it out of its pot and inspecting the roots. If there are grubs, remove them all and repot in fresh compost. If there are not, water-logging would have been the culprit. Remove all rotten roots, and repot in fresh compost. Make sure the pot has a hole in the bottom, never allow the plant to sit in water, and be careful not to overwater this time. It may survive, if it hasn't lost too many roots and you take good care of it.
You will need to remove the flowers and fruits if you want the plant to survive, though. It won't be able to support them, anyway, on what little roots it doubtless has left.