Errors in powers automate : The 'inputs.parameters' of workflow operation 'Add_a_new_row' of type 'OpenApiConnection' is not valid. Error details: input parameter

 

Here the input formula or the filed value is not in the expected format. 

Here the Flow is expecting either a String value or Date-time value. 

You can declare a string at beginning of flow and use append to string to store and pass the value. 

or use formula to convert it into specific date format by using the below formula : 

addDays('01/01/1900',sub(int(items('Apply_to_each_2')?['Date field name']),2),'dd/MM/yyyy')

Another Error : 

The input body for trigger 'manual' of type 'Request' did not match its schema definition. Error details: 'Invalid type. Expected Integer but got String.'.

Sometime the flow may give this error after a long time or when it is run by other user: 

Just duplicate the flow and make it as main flow fixed this issue.