Depending on the smartphone type, your device has the function that mobile data is automatically used again in case of poor WLAN connections or no Internet. Check the display of your device to see if the WLAN icon is shown or if mobile data such as LTE, 3G, H, H+ is used.
If the smartphone is connected to the WLAN, a WLAN icon appears in the display. Only then can the WiFi products be trained in the same WLAN network.
Alternatively, you can deactivate the option "Automatically use mobile data in case of poor WLAN" on your device until the WiFi product is set up.
Make sure that the smartphone is connected to the same 2.4 Ghz WLAN as your brennenstuhl®Connect product.