Question about Strong 4G LTE 350M WLAN Router

Hello Unfortunately I can't get the device configured. The SIM cards are active with Swisscom, as well as at the top right in the status (SIM card is also active, displayed). As soon as I set/save the APN default settings with Swisscom access - it turns blue "Broadband connect" at the top of the status list and then falls back to the red X - result "No Service". Can someone maybe help me? Best regards Dieter