Generate Renewal Order button is missing for a domain registration subscription.
The plug-in the domain was registered with was deleted or uninstalled. To check that, please go
Top > Service Director > Domain Manager > Plug-ins > Plug-in name
There will be the message
Plug-in template files are deleted or not installed. Operations with this plug-in configuration are disabled. Please restore plug-in template files, or install the corresponding plug-in.