I had the same problem, to fix it i found that in .../openstack-dashboard/openstack_dashboard/api/glance.py the default version of 'def glanceclient(request, version='1')' is 1 i changed it to 'def glanceclient(request, version='2')' rebooted apache2 "service apache2 reload" and it worked

It seems that there's a little error on the OpenStack official documentation (https://docs.openstack.org/mitaka/install-guide-rdo/horizon-install.html#install-and-configure-components (https://docs.openstack.org/mitaka/ins...)) for Mitaka. Using API version 2 for image is implemented from the Newton version. So you have to change the configuration in the local settings of the dashboard (/etc/openstack-dashboard/local_settings) and make the use of the Openstack API version 1 for image the restart httpd service.

OPENSTACK_API_VERSIONS = { "identity": 3, "image": 1, "volume": 2, }