Disable 5GHz

There is absolutely nothing wrong with your advise vajim 

When you think about on how virtually all[*1] these discovery processes work, you will see that a factory default or reset IoJ will put up some hidden SSID (open, secured with some shared security, or with security key related or derived from to the BSSID AKA. radio MAC), and the App will put the previous active SSID (including the security key on Android, on iOS the user has to enter it because it's not readable by an App AFAIK) is pushed to the IoJ wireless client, so it will hopefully be able to connect to the normal SSID. At no point (!!!) having the mobile mobile phone connected by 2.4 GHz radio is required. This strange idea comes from the time where people had different SSIDs and security configs for the different radio bands - that's why some crappy Apps check if-connected-by-2.4GHz-go-ahead-else stop code in place. These App designers wanted to avoid that wrong SSID and security (from the 5 GHz radio config) is pushed to the device. This problem does not exist on a Mesh system with single SSID and security setting over all APs. Some slightly enhanced apps allowed to continue regardless, other Apps silently avoided to push the what-they-thought-is-5GHz-config-data to the IoJ. 

[*1] Some more advanced IoJ use Bluetooth, some even NFC, for discovery and config programming - this makes the device resp. the radio interfaces on the board (much) more expensive.