Need to enable older LM & NTLM authentication. Since Vista, this has been set to NTLM2 auth only. SNAP servers generally don't support NTLM2 auths.
1) Click Start
2) Click Control Panel (not classic view)
3) Click System & Maintenance
4) Click Administrative Tools
5) Double Click Local Security Policy
6) On the left pane, click to expand Local Policies
7) On the left pane, click on Security Options
8) Now, on the right pane, near the bottom, click on
Network Security LAN Manager Authentication Level
9) On the drop down, change the default setting (NTLMv2 only) to
Send LM & NTLM - use NTLMv2 session if negotiated.
You can also set this through Group Policy if you are on a domain.