Might be SMB1 .
Microsoft broke SMB shares across multiple platforms. We use FreeNas (evaluating Unraid) and also have some really small client environments that are using just plain windows XP machines with open shares. The latest updates of windows 10 (8 too i think) disables SMB version 1 as it says it is a depreciated protocol. We have had to turn it back on in the windows 10 machines multiple times for some of our clients as MS keeps disabling it.
Some other (off site) references :
https://forums.freenas.org/index.php?threads/more-information-on-smbv1-netbios-win10-no-shares-etc.68456/
https://www.reddit.com/r/networking/comments/8qrt8d/psa_recent_windows_updates_disabling_smb1/
https://blogs.technet.microsoft.com/filecab/2017/06/01/smb1-product-clearinghouse/
How to turn SMB1 back on :
https://www.windowscentral.com/how-access-files-network-devices-using-smbv1-windows-10
