I have two Macs, both running Mac OS Sierra. I can ssh from the laptop to the desktop and use Apple's screen sharing to view the desktop's screen from the laptop. I cannot mount the desktop's disks on the laptop. I have Sharing turned on, both AFP and SMB, but I cannot connect via either. I've tried connecting to the desktop via smb://, smb://.local, and directly by its local IP address (and the same for afp://).
ssh <hostname>.local works, so it's not a DNS resolution issue.
The specific error I get is:
The server may not exist or it is unavailable at this time. Check the server name or IP address, check your network connection, and then try again.
Edit: I should mention that when I try to connect by selecting the machine through the Finder sidebar, it doesn't connect, and clicking "Connect As" fails before getting to the password screen.