Can't connect to SMB share after Sierra upgrade After the upgrade to Sierra on my MacBook Air, I'm unable to connect to the NAS on my home network through Samba. When I try Connect to server and enter:

smb://x.x.x.x/MEDIA/

I get an error saying "this file server will not allow any additional users to log on. Try to connect again later." My Mac Mini, still on OS X 10.9, can still connect to the share.
Try connecting with cifs://x.x.x.x/MEDIA/
Worked for me!