Compatibility Report

• Name of the game with compatibility issues: Proton Experimental itself fails to update (blocks Cyberpunk 2077, Dead by Daylight, and any game using it as compatibility tool)
• Steam AppID of the game: 1493710

System Information

• GPU: NVIDIA GeForce RTX 3070
• Video driver version: nvidia 580.159.03
• Kernel version: 6.17.0-35-generic
• Link to full system information report as Gist https://gist.github.com/Boozzah/fbdd0d0945930413a272af62381f88c6
• Proton version: Proton Experimental

I confirm:

• [x] that I haven't found an existing compatibility report for this game.
• [x] that I have checked whether there are updates for my system available.

Symptoms

Proton Experimental cannot complete its own update/manifest check. Steam's content_log.txt shows a repeating, never-succeeding error:

Failed to get manifest request code, 'Access Denied'
App: 1493710, Depot: 4862111, Manifest: 5497140658785823969

This happens on every scheduler cycle. Steam's UI surfaces this as a generic "No internet connection" error — both as a queue download failure and as an instant "An error occurred while launching this game: No internet connection" when launching any game set to use Proton Experimental as its compatibility tool (confirmed with Cyberpunk 2077, AppID 1091500).

Network connectivity is confirmed fully working: verified reachability to current Steam CM servers (via GetCMListForConnect API) and CDN endpoints (Akamai) with curl/netcat, confirmed successful Steam login in connection_log.txt, and confirmed Steam Store/Community pages load normally. This is not a network, DNS, firewall, or ISP issue — it is isolated to this specific depot/manifest request being denied server-side.

Running "Verify integrity of game files" on Proton Experimental completes with "0 files failed to validate and will be reacquired" but does not resolve the manifest request failure — the same Access Denied error recurs immediately after.

Workaround: switching the affected game's compatibility tool from Proton Experimental to a stable numbered Proton version (Proton 9.0) resolves the launch failure entirely, confirming the issue is isolated to Proton Experimental's own depot/manifest and not a general compatibility or network problem.

Reproduction

1. Have Proton Experimental installed and selected as the compatibility tool for a game (e.g. Cyberpunk 2077).
2. Launch the game, or wait for Steam's background scheduler to attempt updating Proton Experimental.
3. Check ~/.steam/debian-installation/logs/content_log.txt — observe repeated Failed to get manifest request code, 'Access Denied' for App 1493710, Depot 4862111.
4. Game launch fails immediately with "No internet connection," with no game or launcher window ever appearing.
5. Switching the game's compatibility tool to Proton 9.0 (Properties → Compatibility) allows the game to launch normally, confirming the issue is specific to Proton Experimental's depot, not the game or general network connectivity.