Reporting API Error: { code: null, description: 'could not extract ResultSet ...'}

I have encountered this error that is not mentioned anywhere on this site when I used Reporting API on my live account:

{ code: null,
description: 'could not extract ResultSet; nested exception is org.hibernate.exception.GenericJDBCException: could not extract ResultSet' }

The GET request I sent was:
api.payeezy.com/transactions?start_date=20160415&end_date=20160418

I have successes with all other APIs (Credit Card Payment & Search for Events) on my live account.

Thank you.