Remote API doesn't work if you have Pretty URL disabled.

Steps to reproduce:

1. Be sure that you have the Remote API (XML-RPC & SOAP) enabled (Cog Icon > Further Configuration).
2. Access the API: http://your_confluence/rpc/soap-axis/confluenceservice-v2
3. You can see it's working.
4. Now go to Manage Add-ons and find the "Atlassian Pretty URLs plugin" and disabled it.
5. Now try to access this URL again: http://your_confluence/rpc/soap-axis/confluenceservice-v2 you'll see a not found page.

Workaround:

Enabling the Atlassian Pretty URLs plugin should fix this problem.