Nothing happens when I click the button. I'll attach the complete output.
At the end, the following errors are shown when switching between 'Console' and 'Details':
(virt-manager:3055): GLib-GObject-CRITICAL **: g_object_set_qdata: assertion `G_IS_OBJECT (object)' failed
At line 522 I opened the 'Details' window. Then I pressed 'Connect' a few times. Nothing happened and nothing was shown in the output.
At line 524 I switched to 'Console'.