My serviceberry is 10 years old and the bark is pealing on the old growth. Although some of the branches have died it still has lots of green leaves on the remaining branches and also has new growth from runners.
I am not sure what might be causing the bark to peel on your serviceberry tree. Serviceberry trees, Amelanchier canadensis, are in the rose family and so suffer from the same type of problems as roses do – Japanese beetles, spider mites, aphids, leaf miners, powdery mildew, rust and leaf spot. No bark problems mentioned there.
You say bark peeling, but do you mean bark splitting? The following situation happens most easily on thin-barked trees, which describes the serviceberry. Bark-splitting is thought to result from very cold temperatures on sunny winter days and is often associated with southwest exposure. On bright sunny days the southwest side of the tree heats up, absorbing the heat of the sun. When the sun sets or goes behind a cloud, there is a sudden freezing of the warm tissue. This sun scald results in the death of the exposed bark. I don’t know enough about your situation to confidently say this has happened. From your description, it seems that the rest of the tree is quite healthy. I would prune off the dead or damaged branches and work hard to make sure the serviceberry is as healthy as possible.
They will grow in full sun and part shade, but will flower and fruit better in full sun. They also perform best in soil that is lighter and not loaded with clay. Serviceberries like to be kept consistently moist but not saturated. A 2-inch layer of mulch around the plant will help with moisture retention. Do not allow the mulch to touch the trunk of the tree.
If you continue having issues you can send in a photo to Toronto Master Gardeners to help with identifying the problem.