From MATLAB support (very quick resolution):
As for the error you encountered, I would recommend you checking the rest conditions in the limitation listed on the documentation. According to the example, I believe non-negative definite should be the right one. If you have additional questions, please provide the implementation of the system and the required matrices for us to reproduce this error.
As for the inconsistency between the error message and the documentation, I have informed our internal team, and they will consider to address this issue in the future.