If you can no longer access from Windows 10 a protected application, stored on file sharing location, chances are that this server is still using the SMBv1 protocol, which is no longer supported on Windows 10 version 1803. (no longer installed with default Windows Install).
SMBv2 & SMBv3 (Server Message Block) are networking file sharing protocol included in Windows 10 that provides the ability to read and write files and perform other service requests to network devices.
Although there have been 3 releases of the SMB protocol, there is a chance that you may still have devices running the SMBv1 protocol which is old and insecure. SMBv1 was used by router with file sharing capabilities, Network-Attached Storage (NAS) and other computers running Linux.
As a result, customer may get error messages like “The specified network name is no longer available” or “Unspecified error 0x80004005” when trying to access the files.
Also note that older Windows Server like “Windows Server 2000” and “Windows Server 2003” only support SMBv1.
So if customer that still share files from these old Windows servers, he may need to migrate to a newer “Windows Server” like “Windows Server 2012 R2” or “Windows Server 2016” that support newer version of the SMB protocol.
Note1: there is a way to force installation of SMBv1 on Windows 10 update 1803, but it is not advised to do so, as SMBv1 is unsecure and expose the machine to ransomware (like “WannaCry”) that utilize the SMBv1 vulnerability in order to gain access the system and encrypt data on the hard drive.