Having issues with creator, flow and calendar

Having issues with creator, flow and calendar

So I have made a creator app when engineer puts in the date and time  for when they are going to out on site , this then passes the calendar data to flow and then should populate the inputed data to the calendar.  So If use${system.zf_current_date_time}. it will add the date it's created  and not when they are actually going on site. So I am using this formatDate(parseDate(${trigger.Calibration_Due}, "dd-MMM-yyyy"), "yyyy-MM-dd'T'HH:mm:ss'Z'") for the start andformatDate(parseDate(${trigger.Calibration_Due_Finish}, "dd-MMM-yyyy"), "yyyy-MM-dd'T'HH:mm:ss'Z'") for the end date but I keep getting "Zoho Calendar says "start pattern not matched."". What am I doing wrong.
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