This article covers methods to resolve "iisnode encountered an error when processing the request" error.
Basically, this iisnode error triggers when the application pool doesn't have enough permissions to write to the current folder.
Therefore, you need to Allow, 'Full Control', for user 'IIS_IUSRS', from 'Advanced Security' upon right clicking your application root directory.
This error simply denotes that Your application pool doesn't seem to have enough permissions to write to the current folder.
1. You can either edit the permissions to give the IIS_IUSRS group write permissions to that folder
2. Go into the advanced settings menu and under Process Model -> Identity change the user account to a user that already has write permissions.