Gloxinias do best in warm temperatures. They stop growing
in temps below 60 degrees. They require lots of very bright indirect light with a few hours of early or late day direct sun. Keep the soil evenly moist by watering thoroughly only when the top half-inch of soil is dry. Keep tightly potted for best growth and flowering.
I suspect keeping the soil may be part of the problem. Do let the soil dry out some between waterings.
In the fall, gloxinias need to go into a dormant period during which their leaves all die back. It prefers cool temps about 60 degrees from then until February. Keep it in a cool, dim place and do not water it all. In February, resume watering and place it in a bright location. flowers
usually appear from May to September.
Gloxinias can be propagated by leaf cuttings - something to keep in mind if it looks like it is not recovering.