Hi,
I already have a license for Event Calendar pro and I’m wondering if I need to purchase the whole plugin again to upgrade to the newest version or get a coupon since I already have a license?
When did you purchase your license? It looks like you might have last purchased your license in April of 2013, so if you have not renewed the license at any point since then, then you will indeed have to buy a new license at this time.
Let me know if this helps or if you have any further questions about this!