I cannot establish Wi-Fi connection. Scale keeps displaying SET – Help Center

Please check the following points:

Your smartphone is well connected to the WiFi network you want to install your scale to.
If your router is a dual-band (2.4GHz and 5GHz), make sure your smartphone is connected to the 2.4GHz WiFi frequency band. The HS6 Core scale works only on WiFi 2.4GHz because this frequency better passes through the walls (quite convenient for a device that will usually be placed in a bathroom rather than close to a router).

If your smartphone is also a dual-band (2.4GHz and 5GHz), it may communicate with your router using the 5GHz frequency band automatically and you won't even notice it because some routers use by default the same configuration for both frequency bands (same SSID and same password).
In such situation, you will probably receive "Time out" error in the app after entering your WiFi password and scale will keep displayed SET.

To avoid this kind of experience with dual band routers, the practice is to configure 2 separate WiFi networks. Please visit the online support of your Internet Service Provider to know how to distinguish the 2 WiFi frequency band of your router.

Tip - Indicate in each SSID (name of your WiFi networks) the frequency used. For instance: Mynetwork2.4 and Mynetwork5.
Make sure the scale is not to far from your router.
Make sure your router complies with the following technical specifications:

WiFi frequency band: 2.4GHz only, 802.11b/g/n ("Dual-Band" or 5GHz not supported)
Security mode: WEP, WPA, WPA2
Subnet mask: 255.255.255.0 only
Broadcast of SSID: Enabled (the scale can't be installed if SSID is hidden).
Format of WiFi password: cannot contain "," or "." and must be less than 32 characters.
If you have set up a MAC address filtering, make sure you have added the MAC address of your scale. The MAC address is partially printed below the QR code. Add ACCF23 before the 6 other characters visible on the scale.