Error: The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel
When creating a Web application in ArcGIS Server Manager > Add Layer > Add Server > Access secured services, after providing the user name and password from the SQL Server Security database, the following error message displays:
"Error: The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel".
Typically, to be able to use security in ArcGIS Server Manager, SSL is required. If this error displays in ArcGIS Server Manager while trying to add secured Map Services as layers, it indicates that SSL is not set up to trust the certificate.
Solution or Workaround
In Windows, select Start > Run. In the Run dialog box, type 'mmc'.
In the MMC console select File > Add/Remove Snap-in...
Select 'Certificates', and click 'Add'.
In the 'Certificates snap-in' dialog box, select 'Computer account'. Click 'Next'.
By default 'Local computer:' is selected. Click 'Finish'.
Click 'Close' in the 'Add Standalone snap-ins:' dialog box. Click 'OK'.
Open a browser and type in 'https://<Servername>'.
The following message may display: 'There is a problem with this website's security certificate.' Select the 'Continue to this website (not recommended)' option. Click the View certificate details. Copy the details to a file. Save the file onto the desktop, and accept defaults.
Note: The file can be named something like, yoursevername.cer.
Close the certificate dialog box.
Go back to the MMC console. In the Console Root dialog box, double-click to expand 'Certificates (Local Computer)'.