Troubles with the Nop.Plugin.Payments.Robocassa plug-in

Looking at the source code of the plug-in and its Configure method, it seems that there's an issue with the configuration file:

var config = WebConfigurationManager.OpenWebConfiguration("~");
model.RobocassaRequestUrl = config.AppSettings.Settings[RobocassaPaymentProcessor.AppRequestUrl].Value;
model.RobocassaLogin = config.AppSettings.Settings[RobocassaPaymentProcessor.AppLogin].Value;
model.RobocassaPassword = config.AppSettings.Settings[RobocassaPaymentProcessor.AppPassword].Value;

Either it can't open the "~" config or the corresponding AppSettings are missing. Should I add them manually somewhere (webconfig?) or it tries to access the wrong config file?

OK, I added those missing settings into webconfig file and now the page opens with those settings! However, when I modify them and try to save, I get the following error:

An error occurred loading a configuration file: Access to the path 'D:\HostingSpaces\z2443251\stester.ru\wwwroot\0jucovcz.tmp' is denied. (D:\HostingSpaces\z24534451\stester.ru\wwwroot\web.config)

But the permissions are correctly set to Read/Write for the web.config file. Not a big deal, cos I can edit the web.config manually.

Thanks, it works now.