Slava Murygin troubleshoots connectivity issues with SQL Server on Linux:
After you enter SA password you have to get “vNext” version of your SQL Server.
If you did not get the correct response you might have following problems:
I) Wrong SA password. To fix it, just re-configure SQL Server.
II) SQL Server Tools are not installed.
III) Typo. Check your syntax.
The troubleshooting process is a bit different from SQL Server on Windows, but it’s still pretty straightforward.