By default Microsoft Windows Server only allows clients to access it via file manager (SMB access) using the name of the server. It will not allow you to use an alias e.g. a CNAME alias setup in the DNS server records.
To rectify this follow instructions in this Microsoft article:
This opens up all sorts of possibilities e.g. for SQL mirroring we can give servers names like SQL_Principal, SQL_Mirror, SQL_Witness rather than their actual names which means if we bring a new server online we can simply change the DNS record to the new IP of the server. Or our Exchange server has an alias of Exchange and all our Outlook clients point to Exchange on our domain rather than the actual server name – again a simple DNS change is all that is required to swap servers.