Troubleshooting
Getting "This page can't be displayed" when opening modal dialogs
Reason
It normally happens when the security level for the trusted sites is set to low, medium-low and medium. Internet Explorer avoids in this case that the content from IFrame is loaded.
Solution
You have to add the app url from Collaboration Manager 365 and the tenant url to the trusted sites from Internet Explorer.
Needed Information:
Adding these urls to the trusted sites:
To finalize close and reopen the browser. You should now be able to use our modal dialogs.