Have you verified that the pin in the trailer connector is OK. Have you checked the connector on the back of trailer connector? Have you checked for power at the connector with a meter or test light or trailer connector tester?
The left turn pin is the one on the extreme left when looking into the connector.....I think it's even labeled on the outside of the cover (if it's OEM).
Are you sure the fuse is good.? Should be Fuse 46 (15A). If yes, when the left signal is on, can you hear a clicking from a relay in the IPM.
If no, you might have a bad relay (unlikely) or a bad FCM (Front Control Module).
If yes....just replace the fuse (46) just to be 100% sure. Else it is likely a wiring issue between the IPM and trailer connector.