samba: it seems that SMBv2.1 without encryption does not work on Windows Server 2012 R2

While we upgrade all of our Windows 7 to 10 machines, we need an SMB share on a Win12R2 server to support unencrypted connections.

We have:
SMBv1 disabled
Encryption Enabled
Set RejectUnencryptedAccess to false

The expected result would be:
Windows 10 clients would use SMBv3 by default
Windows 7 clients would use SMBv2.1 without encryption.

However, in Windows 7, we simply cannot log in when encryption is enabled.

Any help would be appreciated.

Thank you!