Flow checker has no error.
When save, it shows error: Flow save failed with code 'OpenApiOperationParameterValidationFailed' and message 'Input parameter 'item' validation failed in workflow operation 'Create_event_(V4)': The parameter with value '"@outputs('Create_item')?['body/BookTime']"' in path 'item/start' with type/format 'String/date-time' is not convertible to type/format 'String/date-no-tz'.'.
The "BookTime" is a DateTime field and its format "yyyy-MM-DDTHH:mm:ss"
I attach the screen for your reference.
Thanks.