When you see a red bar with an error code that ends at -2006, it is most likely your web-app cannot access the camera or the microphone.
You can view and change this by following the steps below.
Go to Settings and then press Advanced. Here you will find a button 'manage permissions'. Click it and in the next screen you can see which apps have which permissions.
Click on op Alterdesk and change the permissions accordingly.
Open Safari and go to the web-app. When you go there, go to Safari's prefferences and open the Webistes tab in the next screen. Here you can choose either camera or micropphone. Select the relevant device and make your changes.