Answer: Ficus normally go through a spring growth spurt in response to the longer days and resulting better light, so I would expect it to show some nice growth in a bright location with ample light.
Two possible "invisible" explanations for why this may be happening are that the plant might simply be a dwarf variety or it may have been treated with a growth retardant prior to your purchasing it.
Another possibility is that the roots have remained entwined tightly in their original potting mix rather than growing outward into the soil added at repotting, thus causing a natural sort of bonsai or dwarfing effect. To check for this you would need to unpot it and look closely at the roots. If this is the case, you would probably see other indications of the plant needing repotting, such as wilting/drying out very quickly or poor coloring, in spite of the larger pot size. If you find this, you can try to unwind the roots or try root pruning to try to stimulate the roots to grow outward. When repotting, try to match the original soil mix texture or composition as closely as possible, do not move to a drastically larger pot but instead go up just a size or so, and take care when watering so as not to accidently overwater until the plant has rooted through the new mix.
Finally, this plant is very sensitive to salt and stunting could be a symptom of excess salt in the soil, possibly from fertilizing or from using water that has gone through a home water softener system. To correct that, try leaching several times with plain water. Take care not to exceed label amounts when fertilizing also -- too much is worse than none at all.
I hope this helps you trouble shoot.
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