It is supposed to be on the ROOT of the card. no folders needed. Unfortunately, I’m not sure how i could help more. The only way to debug it is to be connected to it (unless you wire up a serial debugger to it). I saw another thread that said they had to change routers or router settings. You might look there or ask that person.
This person got it working
This person didn’t confirm they got it working
However, Tridge and OlivierB have both done this because they showed it at some drone show 2 years ago. Also, make sure you have the latest SV firmware for the Sonix. One of the threads stated they fixed wifi station mode at some point.