If you have interest, I can help you get it turned around. The leaves are saying the plant has been chronically over-watered, so I'll leave something below about how to use a 'tell', which should help you figure it out. Also, the plant's o/a appearance isn't one that reflects particularly good health. That in itself isn't a problem unless there is a fungal infection or other root issue (nematodes?).

What was the condition of roots when you potted up? Should I assume you didn't do a full repot which includes bare-rooting, root pruning, and a complete change of soil? What did you use for a potting soil? It may be the medium is so water retentive the roots cannot get the air they need to function.

My suggestion is (assuming you didn't do a full repot), return it to the pot it was in and get your watering under control, start fertilizing regularly. I have 30-40 ficus bonsai and this is what I use on all my trees:

Ficus tolerate tight roots reasonably well, so it's not going to be as though its vitality is in jeopardy resultant of returning it to the pot it came in.

It's possible the loss of foliage is related to something that occurred prior to your purchase. Once it starts showing new growth I'll help you devise a plan that will keep your tree safe. In the meanwhile, The following info should be of interest;

An Overview of Good Growing Practices

Caring for Ficus in Containers

Using a 'tell'

Over-watering saps vitality and is one of the most common plant assassins, so learning to avoid it is worth the small effort. Plants make and store their own energy source – photosynthate - (sugar/glucose). Functioning roots need energy to drive their metabolic processes, and in order to get it, they use oxygen to burn (oxidize) their food. From this, we can see that terrestrial plants need air (oxygen) in the soil to drive root function. Many off-the-shelf soils hold too much water and not enough air to support good root health, which is a prerequisite to a healthy plant. Watering in small sips leads to a build-up of dissolved solids (salts) in the soil, which limits a plant's ability to absorb water – so watering in sips simply moves us to the other horn of a dilemma. It creates another problem that requires resolution. Better, would be to simply adopt a soil that drains well enough to allow watering to beyond the saturation point, so we're flushing the soil of accumulating dissolved solids whenever we water; this, w/o the plant being forced to pay a tax in the form of reduced vitality, due to prolong periods of soil saturation. Sometimes, though, that's not a course we can immediately steer, which makes controlling how often we water a very important factor.

In many cases, we can judge whether or not a planting needs watering by hefting the pot. This is especially true if the pot is made from light material, like plastic, but doesn't work (as) well when the pot is made from heavier material, like clay, or when the size/weight of the pot precludes grabbing it with one hand to judge its weight and gauge the need for water.

Fingers stuck an inch or two into the soil work ok for shallow pots, but not for deep pots. Deep pots might have 3 or more inches of soil that feels totally dry, while the lower several inches of the soil is 100% saturated. Obviously, the lack of oxygen in the root zone situation can wreak havoc with root health and cause the loss of a very notable measure of your plant's potential. Inexpensive watering meters don't even measure moisture levels, they measure electrical conductivity. Clean the tip and insert it into a cup of distilled water and witness the fact it reads 'DRY'.

One of the most reliable methods of checking a planting's need for water is using a 'tell'. You can use a bamboo skewer in a pinch, but a wooden dowel rod of about 5/16” (75-85mm) would work better. They usually come 48” (120cm) long and can usually be cut in half and serve as a pair. Sharpen all 4 ends in a pencil sharpener and slightly blunt the tip so it's about the diameter of the head on a straight pin. Push the wooden tell deep into the soil. Don't worry, it won't harm the root system. If the plant is quite root-bound, you might need to try several places until you find one where you can push it all the way to the pot's bottom. Leave it a few seconds, then withdraw it and inspect the tip for moisture. For most plantings, withhold water until the tell comes out dry or nearly so. If you see signs of wilting, adjust the interval between waterings so drought stress isn't a recurring issue.

Al

You are correct, I didn't do a full re-pot. When I took it out of the nursery pot, which was badly misshapen from the roots of the ficus, the roots were wrapping into a tight ball and there was almost no soil worth mentioning. I loosened the roots a little but it was super tight. I potted it in Miracle-Gro Potting Mix (I misspoke earlier).

Scotts & MG merged back in the 90s, so I have a good idea what you used. What are your thoughts?

Al

Well, after reading what you said: "That in itself isn't a problem unless there is a fungal infection or other root issue (nematodes?)" and then the feedback I received on a local facebook gardening page: "Too much water and has a fungus" and "Needs more all day indirect sunlight," I'm just going to return it. I'm in over my head and don't have the right spot for it. Thank you for your help!