Check what object you are passing to that input parameter.
Thanks & Regards,
I suspect you have that microflow behind a button on a page. The input parameter is usually the page context (entity in the data view) or the (list of) records selected in a grid or listview. Please check if these input parameters are correctly used when performing the microflow.
Else, could you elaborate more by sharing some images about what you are trying to do? Thanks!