I recently rebuilt my droplet, changing from Apache to Nginx. I did, however, forget about the SSL cert during this process. So I have a cert I purchased from a CA that was working, but now, I'm unsure how to get it working again?
I'm guessing because I don't have a CSR/private key anymore, I may have an issue?
Yes. To continue using your certificate from CA you will likely need to have it re-issued by providing a new CSR. For that I'd recommend contacting their support department.
There is now an option that provides a trusted SSL certificate absolutely free, LetsEncrypt. This guide covers how to set up and configure a new LetsEncrypt certificate on Nginx. The entire request and setup process can be done automatically within your droplet and you can set up a cron job (scheduled task) to automatically renew it without any need to do so manually.
