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!

I had the same issue. I have a linux server with 2 IP's on my local network, one is set as the DMZ ip on my router that I bind public-facing stuff to (just web and ssh server), the other is internal-only like BIND, etc.

Turns out, when I switched my network from 10.x.x.x to 192.168.x.x, I forgot to update my netmask from 8 bits to 24 bits. Once I did that, share worked immediately. This makes sense as smbd/nmbd need a proper broadcast address for discovery. So check your server and make sure that your mask is correct for your the IP block you're using.

Also, try disabling jumbo frames on the server (make sure MTU is < 2000)