| Error Message | Likely Cause | Solution | |---------------|--------------|----------| | "File integrity check failed" | Corrupted UPD download or wrong hardware revision | Re-download from ISP; verify MD5 checksum | | "Upgrade failed – timeout" | Network jitter or firewall blocking TFTP | Disable Windows Defender firewall; use a short CAT6 cable | | ONT stuck on power LED only (brick) | Power loss during bootloader flash | Requires serial TTL recovery (UART pins) or ISP replacement | | "Invalid image signature" | UPD is for H188A but region-locked (e.g., EU vs LATAM) | Request region-specific build from ISP | | Web GUI shows "Upgrade in progress" for hours | Browser WebSocket disconnect | Hard power cycle (unplug 30 sec) – then attempt TFTP recovery |
Open a web browser and enter the default gateway IP: 192.168.1.1 (some regional versions may use 192.168.1.254 ). zte h188a firmware update upd