This is a known issue caused by “Report Server Only Supports SharePoint Default Zone”.
Solution: In the Alternate Access Mappings section of the Operations
tab in the SharePoint Central Administration Web site, configure the
URL you are using for accessing Reporting Services items to be in the Default zone.
Example :
1. Go to Central Administrator
2. Klik Application Management - Configure alternate access mappings
You see in that the Zone is custom, what must we do is click that url and change it to Default