Cannot connect to SQL Server Express 2008 R2

[TimHayes]

I cannot make a connection to my database in SQL Server Express 2008 R2.

I enter my Server Name/Instance; I am using Windows Authentication. Hit OK and I get this message: "Cannot Connect to DBMS"

I have followed the instructions here and still cannot make a connection:
http://support.esri.com/en/knowledgebase/techarticles/detail/35278


I am using ArcGIS for Desktop 10.2.2 (Advanced).

[VinceAngelo]

The instructions have changed since 9.3.  You now need to make sure the Microsoft
Native Client (which is available from the same folder as Desktop) is installed.

- V

[TimHayes]

Thanks Vince. I remember the thread and I have read the document in the link you posted.

I have done everything seemingly correct just like I did before. I still cannot seem to connect to our DBMS Server via Add Database Connection in ArcCatalog.

I checked the sdedc_SQL Server.log file. I found this is the error message related to my problem:

IDBInitialize::Initialize Failed
CAN'T OPEN INSTANCE: sde:sqlserver.
Spatial Engine Connection Failed (-409).
Cannot Get Access to Instance sde:sqlserver

Any ideas?

[VinceAngelo]

I'm an enterprise guy, so I don't have anything to do with Express, but  the
SE_LOST_DBMS_CONNECTION error indicates that you've got fundamental
issues with how Express is set up, or how you're referencing it, or how the
firewall is configured.  I'd recommend you start with basics -- If you can't
use Microsoft tools to connect then there's no chance that Esri clients can.

- V

[AsrujitSengupta]

Just as Vince suggested,

1. try to connect to that instance using SQL Server Management Studio installed on the Desktop machine (if this fails, ArcCatalog won't work too)

2. If the Firewall is 'Turned On' on the database server, disable it to check if that helps. (if this does help, then you can add exceptions as required in the Windows firewall)

Also...
1. is this the only machine facing the connection issue?
2. have you checked the SQL Server Configuration Manager and checked that the required services are running/enabled