Unable to Decrypt data on second computer

Question

I have two applications, Server and the Client, one running from one machine, and the other from a second machine, the server is passing data using a WebSocket connection, t

Answer 1

The Protect and Unprotect methods are only making calls to the DPAPI, which only works across computers if you have roaming profiles enabled, and only then under certain circumstances.

Instead, use a algorithm with a session key which you manage yourself (AES, others...), or better yet: use TLS as your WebSocket (wss://) or Socket transport (SslStream). Rolling your own crypto is just asking for trouble.