Hi @turner111,
A good catch on the object size! You're absolutely right, the Live Corners widget doesn't show up on very small objects, and Illustrator may not allow rounding if the geometry doesn't support it. If needed, try scaling the object up slightly, apply the corner radius, and then scale it back down.
If you notice the same issue happening even on larger objects, do let me know, and we can investigate further.
Looking forward to your update.
Abhishek