Error Connecting to Database from IIS via WCF using Enterprise Library 6

HI, i have and application with an WCF connecting to SQL Server via Interprise Libary 6.0. It Works fine, but when y upload to IIS it has a error messagge "The connection string for the database 'dbConnectionString' does not exist or does not have a valid provider."
Im using Framework 4.5 and Windows 2012 R2.
If I use SqlConnection it Works fine..
Any ideas?
Thanks

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Diego