The error often occurs with the small anyconnect-win-4.10.xxxxx-webdeploy-k9.exe . Instead, download the from Cisco Software Central:
Let me know which Windows version (10/11, 32/64-bit) you're on, and whether you’re using the web‑launcher or the offline installer — I can give you more exact steps. failed to launch downloader cisco anyconnect 4.10
One of the most persistent and vexing issues to emerge with version is the error: "Failed to launch downloader." The error often occurs with the small anyconnect-win-4
The downloader is often cached incorrectly. 32/64-bit) you're on
While less common for the "downloader" error specifically, an incorrect server address can cause the client to fail to initialize the handshake.
Corrupt staging files prevent the downloader from launching.
(related search terms incoming)