API access blocked

API access blocked

I am trying to get employee attendance entries via Zoho People API. Sometimes it works properly, but sometimes I get this error for few minutes.

"
  1. code:7209
  2. message:"API access blocked since threshold limit exceeded. Please try after some time"
"

What is the threshold limit for API requests? I'm sure I didn't exceed any daily limit(if there is any) because I'm getting this error since early morning. Is there a threshold limit per minute or per hour? My request is;

       https://people.zoho.com/people/api/attendance/getAttendanceEntries?authtoken=xxxxxxxxx&date=16-Jan-2018&empId=XXXX