Left turn signal not working

More than likely you have an issue with the smart junction box but we need to start with checking the voltage from the switch to the SJB when you are turning it in each direction.

Basically, the voltage should be sending the signal to the SJB and then the SJB is what turns the lights on.

https://www.2carpros.com/articles/how-to-check-wiring

I attached the wiring diagrams below but I suspect since the switch is new, that the SBJ is faulty and just not sending a good signal when the switch is turned on.

So, once we verify this voltage then we need to then check the signal from the SJB to to the lamps, and I suspect you will find it is not matching the voltage from the switch. Meaning the SJB will be sending voltage to keep the light on or off which means it will need to be replaced.

Please see the wiring diagrams and let's go from there. Thanks

What sjb do I need to buy?

Please see below for the part detail but it appears this is VIN specific as it is ordered and programmed to your specific vehicle.

The best bet is to contact a dealer and just get the part number per your VIN. Then you can order this part from your source and get it programmed if where you are getting it is not able to program it for you.