Can I know how are you restricting the users to not access the communities' sites? The error in the screenshot says "NPE". If you are using any custom code, you need to handle the exception, add a better message to be shown to the end-user.
Also check if the component shown in the error "/libs/social/console/components/hbs/sitecollection" is available in your instance.
In addition to the above steps, checking the error.log would also help you understand the reason for the error thrown on the page