Workgroup names are irrelevant in a home network. They were meant mainly for small business networks where there is no domain controller (and are never used anymore really; Windows doesn't even make it easy to see it anymore), and WORKGROUP is the default workgroup name in Windows so it's most likely what yours is set to anyway. A domain name is important for security (because your user account is only associated with a specific domain, you have to specify the domain when you provide your username to access resources) but user accounts aren't associated with workgroups. It's just used for display purposes, so you can view them in the Network list in File Explorer for organizational purposes.
Insecure FTP connection just means you're not using encrypted FTP (SFTP which uses SSH or FTPS which uses TLS/SSL). Many applications now give you "warnings" like that because there is a strong push to use secured connections for everything possible. If you were connecting to an FTP server on the Internet, secure FTP is important to prevent your data from being intercepted. It's still relevant on a local network like this, but there's less risk as you have control of the network. (You are more likely to know if a rogue machine is physically plugged in, and you can use a secure Wi-Fi password, and the risk of compromised PCs or other devices is lower.) I doubt this device has any options for enabling secure versions of FTP but you can look in the FTP settings.
Assuming the file share is correctly configured on the device, that network error is likely an indication that you need SMBv1 enabled. You can try enabling SMBv1 functionality in Windows.
Open a PowerShell instance as administrator and run this command to enable it:
Code:
Enable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol
If it still doesn't work, you should disable SMBv1 again with this command:
Code:
Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol
And this one will confirm whether it's enabled or not:
Code:
Get-WindowsOptionalFeature -Online -FeatureName SMB1Protocol | Select State
You may have to restart Windows in order to "reset" the connection attempt since it has already failed once, even though you don't have to restart to enable/disable SMBv1. Windows is just weird about things like that sometimes. If it does work, then you'll have to keep it enabled to use the NAS like a drive letter or browse to it in File Explorer. SMBv1 does have security issues, so the security of your network and any PCs and devices connected to it is even more important when it's enabled. The vulnerabilities are trivial to exploit and older OSes or those that are not updated or have no malware protection may have no defenses against being infected with malware that attacks via SMBv1. But in general, a home network should be safe to use it. (Allowing random people to bring their devices to connect to your network is not recommended, of course.)
You should also disable other services that run on the NAS if you're not going to use them, if they have a disable option. They will also be running very old versions of their services, which may have their own vulnerabilities. There isn't much need for FTP on the local network unless you're using an application that can only transfer files to/from the NAS using that protocol (like a backup application perhaps), and the Media Server probably won't be a lot of use (it's used for streaming media to devices using DLNA or UPnP, and organizing them, but it's not useful for general file access), or iTunes functionality. NFS and AFP are also unnecessary.