If the error message “AT ending with error” appears as you described, it may be due to the following reasons.
- the App EUI, Dev EUI and App Key of LoRa E5 do not correspond to those on Helium.
- There is no Helium network coverage around the LoRa E5 with a strong enough signal for the LoRa E5 to connect to the LoRaWAN.