Error code
AC4
Meaning
Your dryer's WiFi connection isn't working
Moderate
What to do
Why this happens
Potential causes include a faulty WIFI module or poor soldering, an issue with the main PBA WIFI circuit, or entry into line test mode following the dry procedure.
How to fix it
Try reconnecting the dryer to WiFi through the SmartThings app. If it won't connect, restart your router and try again.
SourceSamsung service manual / Customer Repair Guide