This paper is mainly used to solve the case based Alwayson the SQL database, Citrix Studio with the following error:
Error: Failed to verify the position of the central configuration service.
No valid Delivery Controller service at the specified location. The reason: The database has refused connection
Before I encountered a problem, the database is just one operation, then the database service is restarted, restart the main priority of the database alwayson restart, resulting in a alwayson failover. So that would be a standby database becomes the primary.
But the problem is, though, like the contents of two databases, but the database is not synchronized login account, auxiliary database is missing DDC computer account. And there will be no automation in the process of adding an auxiliary SQL computer account, so this process is the need to manually add.
So the solution to this problem is to add DDC computer account to the secondary database. 
When the computer account could not get through the search, because the search when the type is a user name instead of computer accounts, so here to fill in by hand. 
The domain name of the computer account and fill in underlined, followed with $ ending.
For example, your domain name is abc.loc, DDC computer named dc1
then it should be written as abc \ dc1 $
computer account all need to be logged in to add again, specific account can refer to the original list of the main database, because All database that has the computer account. After the addition, re-open citrix studio can be opened.