The angle between the support faces is too large.
When the angle between the two support faces is large, the chamfer face appears to be another face like the support faces, rather than a chamfer. The error message appears when the angle between the support faces exceeds 137°.
Example
If the angle between the support faces is large, the chamfer edge angle is also likely to go out of range. FeatureWorks checks for edge angle errors before checking for support angle errors, and stops checking when it encounters an error. If FeatureWorks encounters an edge angle error, you see a message only about that, even if the 137° limit for support angles is exceeded.