I am not familiar with auto-renewals myself. We only use manual renewals in our organization. However, I did come across this thread that may be helpful to you.
What we recommend is to extend the maximum number of renewals and leave the expiration date as it is and then publish. During the nightly processing, the system will reopen the workspace and renew the contract. If this does not work I would recommend logging a ticket with support as to why the process or scheduled task is not working in your environment.