SQL Server Pre-Login Handshake Acknowledgement Error [duplicate]
Had a similar problem with SQL Express 2014, turned out to be a Windows Firewall problem, some of our Servers have SQL 2005/2008 on them, all with the Windows Firewall disabled.
Made the change on my PC and it worked perfectly afterwards!
Thanks
Brendan
I ran into an issue similar to this myself a few months ago.
For me, enabling TCP/IP for both IPV4 and IPV6 in SQL Server Configuration manager fixed the issue. I have also seen this occur even when IPV6 is not installed. Oddly enough, I've even experienced this behavior even when I only specify IPV4 addresses?!
Had the same problem/error msg. For me, it's the firewall settings on server. Make sure TCP port 1433 is open for incoming traffic.