Rust01

Your issue is that the machine your server is on is not configured properly.

I'd suggest checking on your server for the MONO_TLS_PROVIDER environment variable to see if/what it is set to. The issue you are having is not really related to Oxide itself, just that something is set on your server that is preventing the Mono version that comes with the game from connecting to any site using TLS for their HTTPS connection.

The URL we use with downloading our plugin compiler (Compiler.exe, Compiler.x86, and Compiler.x86_x64) is https://nyc3.digitaloceanspaces.com/umod-01/ which supports TLS 1.0, 1.1, and 1.2. We've been using this URL for at least half a year at this point, so we know that it isn't an issue with the URL as it is actively used daily during installs and update checks to the compiler.

You'd need to resolve that issue for it to work right. If you are using a hosted service, please contact your host.