If the process fails, the failure details will be shown in the lower portion of the Image Upload tab.
If the virtual machine has not been deployed, then depending on the error reason, you may need to re-upload a new one or attempt to redeploy.
If the VM has been deployed, but the conversion of gold pattern fails, the VM could appear in the “Imported Desktop” pool, or “Reserved Desktop” in pattern management. Locate the VM there and prepare the image manually using Console Access in the Helpdesk Console and the Administration Console. This allows you to skip re-upload/deploy, which could take a long time if the VM image is large.