I don’t know which client you use, but if you use
certbot certificates it will show all the certificates - expired and valid. If you’re still using the expired cert and do have a valid one, install the valid one.
But IMHO, this sounds like a problem to be solved at community.letsencrypt.org.
One thing to take note of: LetsEncrypt was designed to automate your renewals. If you run if with the
certbot manual command, then you have to manually renew every 60-90 days. If you use
certonly, once you’ve created the cert, you’ll have to install it yourself.