This is an old issue, but I finally solved it. It turns out our proxy server doesn’t by default allow the PROPFIND http method, (over HTTP or HTTPS). Maybe this info is of use to other people. More info here: https://serverfault.com/questions/314414/is-our-company-firewall-blocking-http-propfind
In the Modeler you can configure a proxy server via the Menu: 'Edit-> Preferences... -> Advanced Tab'
That configures only the proxy username and password. I don't see any references to the server host.
You don't see a place to input the server host in the Modeler interface because we use system settings for determining the proxy server. Apparently, this doesn't work in your case :)
Since you're using Modeler version 7.18, you could try to manually specify the proxy server settings for SVN client that we use. Please do the following:
If the servers file appears to be empty or almost empty, here are the default proxy settings that you would need to alter:
[global] http-proxy-host = defaultproxy.whatever.com http-proxy-port = 7000 http-proxy-username = defaultusername http-proxy-password = defaultpassword http-proxy-exceptions = *.exception.com, www.internal-site.org
Kindly let me know if this works for you.
P.S. Also, if this doesn't work, please locate the log.txt file in \Users\<username>\AppData\Local\Mendix\log\7.18.0 folder and attach it to your response in this thread. Thanks!