As of the last Chrome browser version the showModalDialog API is no longer supported. This means when you use Chrome to access Outlook Web App, the Exchange Admin Center, SharePoint, Microsoft CRM, and other online services, some pages or windows won't appear as expected - basically any page that comes up in a separate window and keeps focus until it's closed.
Last spring, Google announced they were planning to stop supporting the showModalDialog API and announced in July that it would be disabled in the next release.
Administrators can enable modal dialogs (until 4/30/2015) by setting a registry key.
String value: 1
Value data: ShowModalDialog_EffectiveUntil20150430
If you don't want to edit the registry, you can download this ready to use registry file. Double click to run it and add the value to the registry. (If your browser saved it with a txt extension, change it to reg first.)
Certain pages or windows don't appear in Outlook Web App or Exchange Admin Center when you use Google Chrome (MSKB)