SVN E200015: authentication failed

Hello

Description:
I get following error when I want to build our game for web:

• Unity Version: 5.4.0f3 (Configuration in Unity Cloud Build: "Always Use Latest 5.4")
• Source Control: SVN via HTTPS and a custom port (own server with a certificate from here: https://www.sslforfree.com)
• SVN-User: Firstly tried with a user with read-only permissions, then with write permissions
• Build target: WebGL
• Plugins: No relevant plugins with post-build behaviors used (as far as I know)
• Project name: In Unity Cloud Build the project is called "Kortek"
• Local Build: A local and fresh SVN-checkout works fine.

Research:
I found the following threads, but I coudn't find a useful answer yet:

• https://forum.unity3d.com/threads/b...us-code-404-exception-stacktrace-none.341199/
  
• https://forum.unity3d.com/threads/e...when-trying-to-build-from-private-svn.431471/
  
• https://forum.unity3d.com/threads/svn-authentication-cancelled.406503/#post-2792503

Images:
I've also attached some images

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I hope somebody can help me Thank you and have a nice day!

 

Thanks @Zwer99! I'm about to DM you

 

@Zwer99 I was unable to DM you. Could you either send me a message, or turn on your inbox? Thanks!

 

@SophiaC thanks for the reply! I think I could turn on my inbox and also started a conversation with you (I don't know if that worked).