Look at the sticker underneath your router. Ensure it explicitly states EchoLife HG520b . Applying firmware meant for the HG520s or HG532 series will ruin the device.
Connect your computer to the router via an Ethernet cable (avoid updating over Wi-Fi to prevent data corruption). huawei echolife hg520b firmware upgrade download verified
that a newer firmware addresses (e.g., Wi-Fi dropouts or PPPoE reconnection bugs). The HG520b is an ADSL device – if you’re on fiber or VDSL, this router is obsolete. Look at the sticker underneath your router