Hi Rami,
If you don’t have a page selected in the Unassigned tray (which will appear if you expand the menu in the lower left of the screenshot you’ve shared) when creating a template from a page, the system will sit the “Processing” window indefinitely. This behavior has been filed as a bug. For now, please be sure you have a page selected in the Unassigned tray when performing this action. If you’re aiming to create an entirely new template from scratch – or to duplicate an existing template – you will want to use the “Add Template” feature instead.