This error is quite common and has numerous causes. I’ve used samba on Linux for a long time. I’ve never seen this error. When I finally did have the error I went looking for a cause. A lot of people had answers but none of them resolved the issue for me.
What I was doing was setting up a Proxmox virtualization server. It uses LXC. I also have a VLAN that doesn’t route to the inside LAN. I needed to send backups of containers from the virtualization server to a backup server.
Since I had UFW installed and configured I checked to see if the ports for SAMBA were open. They were not. I do not just open ports to any computer, even internally. So, I opened the necessary ports by adding them to allow access from specific computers.
Further, you should make sure the account you are using on target machine has been added to samba use by: smbpasswd -a username