Security updates KB4480960 and KB4480970 for Windows 7 SP1 and Windows Server 2008 R2 SP1 released on January 8, 2019 (January's Patch Tuesday) cause network shares to be inaccessible under certain circumstances: The issue is triggered only if the user attempting to make the connection is an administrator on the machine that hosts the Share. If the user is a non-administrative user on the device that hosts the share, the connection works fine.

Workaround:

If you are facing this issue, follow the steps mentioned below on the computer which hosts the share.

• Run the following command from an elevated command prompt: reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\system /v LocalAccountTokenFilterPolicy /t REG_DWORD /d 1 /f
  

• Reboot the PC.