The problem turned out to be the graduation date, which was later than the "completion of degree requirements" date. The OP applied less than a year from actually graduating. This is unfortunately, not a rare mistake.
Students be warned - You may think "convocation" is just a ceremony, but that is usually when your degree is awarded, (i.e. you graduate). Until you graduate, your experience will not count. You CAN apply for your PGWP before you graduate, that's what happened here, and is a source of confusion.