For my ZNC server I use a SSL cert from Lets Encrypt. Recently, one of the certificates in the root chain expired, so I was able to run a command on my server to update the root chain to a trusted certificate which now shows as not expired (Source: https://blog.devgenius.io/lets-encrypt-change-affects-openssl-1-0-x-and-centos-7-49bd66016af3).

However, I'm still getting the error about the certificate has expired. Here's screenshots of the certifcate path and error message. https://imgur.com/a/s72BDlC

Thanks for posting. This issue has hopefully been fixed in the latest release which can be downloaded from the mIRC website.

The update fixed it! Thank you for your hard work!