You can do an OS reinstall on the NAS. This will reset some settings to default, such as Internet protocol settings and the administrator password. You may check this KB article for the steps on how to access the boot menu and select the OS reinstall option.
The default credentials of the RN104 is admin for the username and password for the password.
That thread generally is specific to Windows 10. But Microsoft has been making changes to the policies on guest access.
Try running the command prompt (CMD), and type
net use * /delete
net use t: \\nas-ip-address\data /user:admin nas-admin-password
using the actual NAS ip address and admin password. If your admin password is password, then change it to something else before you try this test.
The first command terminates any open network sessions - it will either tell you that there are none, or prompt you to confirm. If it prompts, let it proceed.
The second command attempts to mount the NAS data volume as drive letter t. Let us know if that command works (and if not, what error you get).
If the command does work, then one option is to go into the Windows Credential Manager. Delete any credentials that it has for the NAS, and create a new one. If you access the NAS by both it's IP address and by it's host name, then you will want to enter one credential for each.
