there was a discussion not long ago if this support forum for ownCloud is the best place to ask for support of non-ownCloud related topics like the renewal of certificates within a web server:
Personally i can’t help you with this topic and others seems to be not able as well as no posts where made by other users. Based on this i would suggest to try searching for a tutorial on the internet on how to configure and/or renew SSL on your web server.