It shows "No boot source available" when installing from ISO

1. Create VM from template and select Boot from CD
2. Select http and input ISO link there
3. Click customize
4. The "Start this VirtualMachine after creation" button is in grey
5. Click "Create VirtualMachine" button
6. "No available boot source" shows
7. Edit the bootable disk in disks tab
8. Select the ISO disk and make it bootable
9. Click the "Create VirtualMachine" button
10. Now the VM is created

"No available boot source" shows when creating VM from ISO

It should use the ISO disk as the bootable disk and no "No available boot source" shows.