The e-mail used for those reminders is coupled to your Let’s Encrypt “ACME” account. It’s completely separate from other stuff like this community forum. So you’ve justly registered a new (and thus separate ;)) account for the forum
How to actually renew depends very much on the way the previous freelancer got the certificate issued in the first place. He could have used literally one of tenths of clients.
So it really depends on how you want to be helped: do you “simply” want to renew your current certificate? Then we need to figure out what client was used to initially get the certificates.
Or you just get a “new” certificate and go from there.
Both of those options actually really need the questions that were presented to you when you opened this new thread (I’ll leave out the two first questions):
My operating system is (include version):
My web server is (include version):
My hosting provider, if applicable, is:
I can login to a root shell on my machine (yes or no, or I don’t know):
I’m using a control panel to manage my site (no, or provide the name and version of the control panel):