Have you checked the Share Permissions and NTFS Permissions? Windows Firewall and Network Settings for Private/Public Networks?
I guees you are in an Workgroup?
I am not a fan of the Microsoft Credential Tresor but you can give User a Password and save the Credentials to the Tresor with the target Hostname/IP also just for testing if this is the Problem.
It could be the problem with no password, but also with permissions.
Maby also try to map it with the cmd (with and without password protected user)
net use Z: \\ServerName\SharedFolder /user:Username Password