Internet Service Providers (ISPs) frequently update their infrastructure (e.g., switching to IPv6 or changing PPPoE standards). An old firmware might fail to negotiate a proper WAN connection, leading to the dreaded "No Internet Access" error.
Do not download firmware from “drivers-updater.com,” “router-firmware.net,” or any random pop-up site. These often contain ransomware or brick your router. tenda f6 firmware update link