System.TypeInitializationException was unhandled
Message="The type initializer for 'System.Transactions.Diagnostics.DiagnosticTrace' threw an exception."
Source="System.Transactions"
TypeName="System.Transactions.Diagnostics.DiagnosticTrace"
The problem was that in the app.config, there is the <configsections> element. There should be only one instance of this element. If there is only one, then it should be the first element in <Configuration>.
If you don't use the SettingsManager class, it doesn't cause a problem.