Avoid random “firmware download” websites from the first page of Google unless you verify the checksums. Many host malware-laden files or outdated beta versions.
Tenda frequently reorganizes its download database. Use the “Download” section of their main site search with the keyword “HG9”. Alternatively, use the Wayback Machine to find archived links for older versions. tenda hg9 firmware link
or disconnect the Ethernet cable during the update. Avoid random “firmware download” websites from the first