Hello Thomas,
The integer in brackets of "Unexpected celltype" exception - which is 5, based on your error text - indicates a cell type which is defined in a Cell class within Apache POI (which is used in the adapter module): "5" stands for cell type error. Apache POI library does not support parsing Excel cells of type error. Having this in mind, please check the input Excel file and search for cells with errors. After Excel file is error-free, please try to process it again.
Regards,
Vadim