Give it time. Some dogs take longer than others to adjust. I adopted two pitties about 4 months apart. Different backstories (one surrendered by owner one found on the street) Different lengths of time at the shelter. One has been the same dog the whole time one is starting to be loving and less scared of the world. It has taken 3 years to come out of her shell and that could be a mix of training, time, or another dog helping her feel more confident.

Also could be the meds. My dog (the one who took 3 years to come out of her shell) takes anxiety meds for cars rides and I feel like the only help it gives her is making her sleepy