The zones may have different cookware detection requirements. A base that suits the smaller area can be too small for the larger one.
What the observation means
This does not automatically prove that the larger zone has failed. The pan's magnetic area may also be smaller than its visible rim.
A useful next step
Check the model's minimum and maximum cookware dimensions and use an appropriate zone. If a correctly sized, confirmed compatible pan is also rejected, report that evidence. Do not use an adapter or increase power repeatedly to force recognition outside the stated arrangement.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.