Please fill out the fields below so we can help you better. Note: you must provide your domain name to get help. Domain names for issued certificates are all made public in Certificate Transparency logs (e.g. https://crt.sh/?q=example.com), so withholding your domain name here does not increase secrecy, but only makes it harder for us to provide help.
Besides that, you seem to have removed all the other important and required questions of the provided questionnaire. Without the answers to those questions, we can’t do anything for you. There is no such thing as a crystal ball by which we can magically aquire the required information. So I urge you to fill in the answers to the questions to your best knowledge:
The operating system my web server runs on 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):
This operating system hasn’t received security updates for almost a year. It needs to be reinstalled or replaced with a new version.
I don’t know immediately whether this is related to your certificate renewal problem, but it might be. @JuergenAuer mentioned that you could be using out-of-date Let’s Encrypt client software that isn’t receiving updates. This could be due to your out-of-date operating system. The out-of-date Let’s Encrypt client application could, in turn, no longer be compatible with the current Let’s Encrypt service.
Is it possible that you could make a plan to replace the operating system on this server with a modern one?