Hi Bertran,
To use this module, you are required to install the Model Reflection module as well. You can download it from the Marketplace, this should fix your errors.
For more information on how to use the Excel Export module, this documentation is very useful: https://docs.mendix.com/howto/integration/using-the-excel-exporter/.
Hope this helps.
This looks like you’ve forgotten to install the MxModelReflection module from the marketplace.
https://docs.mendix.com/howto/integration/using-the-excel-exporter/#download-modules
I hope this helps.