What is condition of rootage? Tight in pot? How long since repot/pot-up? It's usual for foliage to appear healthy even as branch extension diminishes in response to being root-bound. Many other possibilities too. Poor soil is first to mind, possibly a nutrient shortage.

Al

Agreed. How long in the pot. It cannot hurt to repot or pull from the pot, examine, and repot. You can trim the roots a little and put it right back in the same pot, but seeing the roots and condtion of the soil below it will be invaluable. You can do this anytime before it is in-leaf, but the sooner the better at this time of the year. If you still don't see some revival you can post some photos here of the problem leaves and twigs or then use a small amount of fertilizer.

Unfortunately, fertilizer is rarely the answer in maples, but it can assist a healthy one. It usually only compounds problems with a stressed one. And in the situation of root rot or root problems, it can often be deadly.

MJH

Not too long in the pot, maybe four years. It's a BIG pot, at least 8 gallons. Too big to pull it and check.

Also, I note it is leafing out nicely. I'll keep tabs on it.