An error occurred while attaching module (Dynamicweb.Frontend.Content)

System.Data.SqlClient.SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) ---> System.ComponentModel.Win32Exception (0x80004005): The system cannot find the file specified
   at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.Open()
   at Dynamicweb.Data.DatabaseConnectionProvider.CreateConnection(Boolean open)
   at Dynamicweb.Data.Database.CreateConnection()
   at DanskRideForbund.BusinessLayer.Provider.DataProvider.GetCollection[T](SqlCommand command, SqlConnection connection) in D:\a\1\s\DanskRideForbund.BusinessLayer\Provider\DataProvider.cs:line 41
   at DanskRideForbund.DataAccessLayer.HorseData.GetHorsesById(ICollection`1 horseIds) in D:\a\1\s\DanskRideForbund.DataAccessLayer\HorseData.cs:line 120
   at DanskRideForbund.BusinessLayer.Provider.HorseProvider.GetHorseById(String horseId, Boolean includeVfL, Boolean isExternal) in D:\a\1\s\DanskRideForbund.BusinessLayer\Provider\HorseProvider.cs:line 223
   at DanskRideForbund.CustomModules.HorseModule.HorseModuleFrontend.ShowHorse(HorseHelper helper, DataArea dataArea) in D:\a\1\s\Application\CustomModules\HorseModule\HorseModuleFrontend.cs:line 149
   at DanskRideForbund.CustomModules.HorseModule.HorseModuleFrontend.GetContent() in D:\a\1\s\Application\CustomModules\HorseModule\HorseModuleFrontend.cs:line 45
   at Dynamicweb.Frontend.Content.GetModuleOutput(Paragraph paragraph, PageView pageview)
ClientConnectionId:00000000-0000-0000-0000-000000000000
Error Number:2,State:0,Class:20