The FMU export process is strict about signal dimensions, and this error is typically related to a signal that does not meet the requirements for FMU export. I would recommend you to go through your Simulink model and verify the dimensions of all signals, especially those that are part of the interface to the FMU. Make sure that all signals have dimensions that are positive double vectors. For example, a signal should not have dimensions like [1, x] or [x, 1, 1], where x is a positive integer.
Hope it helps!
