Whenever you try to "unbrick" your device or downgrade to Win8.1, the Windows Phone Recover Tool will throw the "Unable to connect to remote server".
Checking the log files, you can see:
2015-07-13 14:54:32Z | 4804 (WindowsPhoneRecoveryTool) | 0x00000004 | WindowsPhoneRecoveryTool.exe |...