Problem with Tunnelbrick : failed to negotiate cipher with server.

[N.Nattanich CDD]

I got this problem and I don't know how to fix it .

2024-04-04 15:43:40.264765 OPTIONS ERROR: failed to negotiate cipher with server.  Add the server's cipher ('AES-128-CBC') to --data-ciphers (currently 'AES-256-GCM:AES-128-GCM:CHACHA20-POLY1305') if you want to connect to this server.

2024-04-04 15:43:40.264787 ERROR: Failed to apply push options

Please find attached Copy Diagnostic Info below.

Thanks.

[Tunnelblick developer]

Please see Tunnelblick 4.

[N.Nattanich CDD]

I'm sorry I already read all of it, but I still not understand, Could you please tell me step by step please ?

[Tunnelblick developer]

You need to do two things:

1. Change the version of OpenVPN/OpenSSL that Tunnelblick is using to connect to your VPN. You may need to try several different versions of OpenVPN/OpenSSL to find one that works with your configuration. My best guess is that OpenVPN 2.5.9 - OpenSSL-1.1.1w will work, but it's just a guess.
   
2. Contact whoever setup your VPN or gave you your VPN configuration and notify them that the VPN setup is insecure and outdated.

To change the version of OpenVPN/OpenSSL that Tunnelblick is using:

1. Click on the Tunnelblick icon in the menu/status bar,
   
2. Click "VPN Details"
   
3. Click on the large "Configuration" button at the top of the window
   
4. Click on to select a configuration on the left side of the window
   
5. Click on the "Settings" tab in the middle of the right side of the window
   
6. Click on the button to the right of "OpenVPN Version"
   
7. Select a version to try.

[N.Nattanich CDD]

OMG It's work!  Thank you very much for your help. :)