Are you sure it is dying or is it just adjusting to the indoor conditions? I have the same problem with my mandevilla...I have to bring it in...it does OK for a few weeks, then starts to lose all it's leaves and eventually looks like a stick by the end of winter...but then it miraculously comes back to life when I put it out in
spring. Overwatering is often the reason for many tropical
plants dying that are being overwintered inside. You might also want to get a humidifier if you don't have one. Hope this helps!