I beat my head against the wall for hours trying to figure out why external storage wasn’t working with my Nextcloud instance after I migrated it over to CentOS 7. All I kept getting was a very unhelpful
There was an error with message: Empty response from the server.
I installed all the libraries multiple times. I tried different versions of smbclient and php-smbclient but the error kept happening! Eventually I decided to check the samba logs of my samba server. Sure enough:
create_connection_session_info failed: NT_STATUS_ACCESS_DENIED
The username and password I was using was correct. I read on some forum (sorry, no link) to put something in the Workgroup field. Voila! As soon as I populated the workgroup field in Nextcloud for my SMB shares, they all worked!