The error says that the property called “Data source” is using a microflow. That microflow expects an input parameter that doesn’t match what’s available on the page. So:

• Does your data source microflow actually need an input parameter?
  • If not, delete it.
  • If yes, model your page (i.e., add a data view) so the parameter is available to the microflow

It is better to remove the parameter while creating the custom widget.

The parameter will be auto generated when you create a microflow