Your smartphone has the function that mobile data is automatically used again in case of bad WLAN connections. Check in the display of your end device if the WLAN symbol is shown or if mobile data like LTE, 3G, H, H+ are used. If your terminal device is connected via mobile data, wait a moment to see whether the terminal device connects to the gateway via WLAN. Only then will a WLAN symbol appear in the display. Alternatively, you can deactivate the option "Automatically use mobile data in case of bad WLAN" on your terminal device until the gateway is set up.