Samba will not accept the credentials

Solution 1:

The Windows 7 network client requires packet signing by default (to prevent man-in-the-middle attacks), and Samba disables packet signing by default. It may be that your client and server are failing to negotiate with each other on this item. So you could resolve it in one of two ways.

Server Side Solution: Enable Packet Signing on Samba

Add the following to your smb.conf:

server signing = auto

Restart the service and try again.

You could also try mandatory instead of auto. Read the docs here.

Client Side Solution: Disable Packet Signing on the Microsoft Network Client

First, open the Local Group Policy Editor:

1. Press the Start button
2. Type gpedit.msc in the Start search box and press Enter

In the Local Group Policy Editor, go to:

Local Computer Policy->
  Computer Configuration->
    Windows Settings->
      Security Settings->
        Local Policies->
          Security Options

Find the policy:

Microsoft network client: Digitally sign communications (always)

If this is enabled, change it to Disabled. Press Apply, restart the computer, and try again.