Configuring High Availability in RD Connection Broker

Configuring High Availability in RD Connection Broker.

Database Connection String:
DRIVER=SQL Server Native Client 11.0;SERVER=WIN-741258963;Trusted_Connection=Yes;APP=Remote Desktop Services Connection  Broker;Database=Testdb

Folder to store database files:
C:\inetpub\wwwroot\App_Data

DNS round robin name (ClientAccessName):
RDSCB01.mysite.com

Error Code:

The database specified in the database connection string is not available from the RD Connection Broker server WIN-741258963.mysite.com.  Ensure that the SQL Server is available on the network, the SQL Server Native Client is installed on the RD Connection Broker server, and the RD Connection Broker has write permission to the database.

C:\inetpub\wwwroot\App_Data\Testdb.mdf exists.

SQL Server Native Client is installed on this server.

RDCB01 exists on DNS Round Robin.

RD Connection Broker has write permission to the database?