It sounds like a pathogen like verticillium that has compromised (but did not kill) part of the tree starting last year or the year before. It's difficult to give a prognosis...it may recover fully, it may stay the same, that section might decline or die, the whole tree might decline and die.

I don't think it's vert wilt. The OP says the tree had fall color early on the stressed side. My experience with vert wilt is that the leaves do just that - wilt. Not color up nicely and drop.

Where is this sugar maple located? Is it a cultivar or native tree? What kind of soil is it growing in? Have you had drought or excessive rains in recent years? Abnormally early leaf change is usually a warning sign of poor or stressed tree health. In my experience, trees showing these symptoms are often suffering root damage - whether it's a girdling root on that side of the tree, a hardiness issue brought on by lack of snow cover/drought, or potential root rot from sitting in heavily saturated ground for too long. It's possible the tree could recover but if it continues the early leaf drop, stunted new spring growth, and branch die-back, its days are probably numbered.

If the buds never break, the branches are dead. Have any pics to share of this tree?

Thank you. I do kind of think it is a girdling root problem. It is a native sugar maple tree that may have been planted haphazardly by the previous owners of the property. I actually cut an exposed root that was girdled around the trunk of the tree a few years ago which could be part of the problem.

Do you know whether new roots may grow to support the existing branches that are effected? We have had a ton of rain this spring, and it has been a lot cooler than usual. Most years, our leaves are out at full peak by May 15th, but this spring we still have catalpa and locust trees with their buds just beginning to open.

Sugar maple “decline“ is common and causes these symptoms. It’s not a specific disease, but as said above, generally a combination of root girdling, compaction (is the tree near pavement?), salt damage, drought stress. Etc.

I’m in an area that’s a bit on the warm side for sugar maples anyway, but the ones that tend to look the best, are ones that are planted in very large yards with plenty of room to spread their roots, and no obstructions from pavement, no exposure to road salt runoff, etc.