In some cases macOS Sierra (Mac OS X 10.12) 10.12.5 may not be able to connect to your Prinergy server without specifying an account name in the path. If SMB://<servername>/<sharename> fails to connect to the server you may have to use SMB://<accountname>:@<servername>.<qualified.domain>/<sharename>, which provides a more complete network path and user name to connect to the server.
Alternatively, if you have File Sharing enabled in the Sharing pane of System Preferences on macOS Sierra, it may cause SMB connections to require the account name in the path. If you don't require File Sharing to be enabled on your Mac, disabling it may revert the behavior in macOS Sierra to allowing connections with the simpler SMB://<servername>/<sharename> path type.