I need to restart the application pool often and get this error:

[SqlException (0x80131904): Cannot open database "cloudpanel" requested by the login. The login failed.
Login failed for user 'sa'.]
   System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection) +1338
   System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection) +159
   System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection) +382
   System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions) +307
   System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry) +198
   System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry) +422
   System.Data.SqlClient.SqlConnection.Open() +199
   System.Data.Entity.Infrastructure.Interception.InternalDispatcher`1.Dispatch(TTarget target, Action`2 operation, TInterceptionContext interceptionContext, Action`3 executing, Action`3 executed) +104
   System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.Open(DbConnection connection, DbInterceptionContext interceptionContext) +503
   System.Data.Entity.Migrations.DbMigrator.ExecuteStatementsInternal(IEnumerable`1 migrationStatements, DbConnection connection) +334
   System.Data.Entity.SqlServer.<>c__DisplayClass1.<Execute>b__0() +18
   System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute(Func`1 operation) +234
   System.Data.Entity.Migrations.DbMigrator.ExecuteStatements(IEnumerable`1 migrationStatements, DbTransaction existingTransaction) +270
   System.Data.Entity.Migrations.DbMigrator.ExecuteOperations(String migrationId, VersionedModel targetModel, IEnumerable`1 operations, IEnumerable`1 systemOperations, Boolean downgrading, Boolean auto) +1227
   System.Data.Entity.Migrations.DbMigrator.ApplyMigration(DbMigration migration, DbMigration lastMigration) +513
   System.Data.Entity.Migrations.DbMigrator.Upgrade(IEnumerable`1 pendingMigrations, String targetMigrationId, String lastMigrationId) +192
   System.Data.Entity.Migrations.DbMigrator.UpdateInternal(String targetMigration) +609
   System.Data.Entity.Migrations.DbMigrator.EnsureDatabaseExists(Action mustSucceedToKeepDatabase) +578
   System.Data.Entity.Migrations.DbMigrator.Update(String targetMigration) +116
   CloudPanel.Bootstrapper.UpdateDb() +460
   CloudPanel.Bootstrapper.ApplicationStartup(TinyIoCContainer container, IPipelines pipelines) +1799
   Nancy.Bootstrapper.NancyBootstrapperBase`1.Initialise() +734
   Nancy.Hosting.Aspnet.NancyHttpRequestHandler..cctor() +44