Hi edadare,

Based on your error message, this issue was caused occurs when the following conditions are true:

• The server is configured for Basic authentication.
• The connection between your computer and the web server does not use Secure Sockets Layer (SSL).

By default, file operations that use Basic authentication over a non-SSL HTTP connection are disabled in Office 2010 and Office 2013 applications.

When Basic authentication is disabled, one of the following events occurs:

• The client application uses a different authentication method. This occurs if the server supports a different authentication method.
• The request fails (for details about what happens when a request fails, see the list in the "Additional symptom details" section).

Please try these workarounds to help you.

Workaround 1:

Try to use HTTPS to instead of HTTP.

Workaround 2:

Connecting a web server by using Basic authentication over a non-SSL connection.

To enable Basic authentication on the client computer, follow these steps:

1. In Windows Vista or Windows 7: click Start, type regedit in the Start Search box, and then press Enter.

In Windows 8: hold the Windows key (WINKEY) + F, highlight Apps in the Menu bar, type regedit in the Search box, and then press Enter.

1. Locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WebClient\Parameters
2. On the Edit menu, point to New, and then click DWORD Value.
3. Type BasicAuthLevel, and then press Enter.
4. Right-click BasicAuthLevel, and then click Modify.
5. In the Value data box, type 2, and then click OK.

Note The mapping is as follows:

0 - Basic authentication disabled

1 - Basic authentication enabled for SSL connections only

2 - Basic authentication enabled for SSL and non-SSL connections

1. Exit Registry Editor, and then restart the computer.

Workaround 3

Update the Registry on the client

1. Start Registry Editor.
2. Locate and then click one of the following registry subkeys:

For Office 2010

HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Common\Internet

1. On the Edit menu, point to New, and then click DWORD Value.
2. Type BasicAuthLevel, and then press Enter.
3. Right-click BasicAuthLevel, and then click Modify.
4. In the Value data box, type 2, and then click OK.

Note The mapping is as follows:

0 - Basic authentication disabled

1 - Basic authentication enabled for SSL connections only

2 - Basic authentication enabled for SSL and for non-SSL connections

1. Exit Registry Editor, and then restart the computer.

More information please read this article:

https://support.microsoft.com/en-us/kb/2123563

Please try these methods and check if the work for you.

Regards,