This certainly sounds like the card shown in the photos from @Vaklin is bad. Not sure what your DIY level is on equipment like the ST16. The card is not too difficult to replace and will likely cure the problem.I apologize for the confusion. I can turn on wifi but when I turns it on, it says it's searching but doesn't find anything

Yuneec ST16 / ST16-Pro Controller 5.8gHz WiFi Video Module YUNST16111SVC
Yuneec ST16 and ST16-Pro Controller 5.8gHz Video WiFi Module -Yuneec Part Number: YUNST16111SVC-Fits Yuneec: ST16, ST16-Pro Controllers-Includes: 1-Wifi Module

They are still offering 15% off now also.