I can not connect to a password protected share from my Mac

Okay. Here is exactly what I have done, per your request:

1. Create a new user called testuser. Group is users. No password is set for this user
2. Create a new share called testshare. Default configuration - Read/Write. Enabled for CIFS and AFP

On windows machine:

Map Network drive:
Attempt 1:
share: \\powers-nas\testshare
user: testuser@powers-nas

Attempt 2:
share: \\192.168.1.2\testshare
user: testuser@powers-nas

Both resulted in the same error:

Error code: 0x80070035
The network path was not found.

Clicking "Diagnose" returns this error message:
"powers-nas" is not set up to establish a connection on port "File and printer sharing (SMB)" with this computer.

Attempt 3:
Allow guest access on the new share
Again, tried Map Network Drive:
share: \\powers-nas\testshare
<no user>
<no password>

Same error message as before.

Also tried connecting by IP.

Also tried to map the drive by choosing Network > Add Network Location > Custom Location:
\\powers-nas\testshare
Also tried by IP:
\\192.168.1.2\testshare

Both resulted in the error message:
The folder you entered does not appear to be valid. Please choose another.

Have I done this test case correctly? Or have I missed something?