there is a KB: https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000POWJCA4&lang=en_US%E2%80%A... with instructions how to enable certificate expiration check.
Unfortunately, I have a mixture of feelings about this feature. While I have not seen anybody complaining about this not being working properly, at least in my case it did not trigger any alert. After several month long TAC ticket, TAC engineer confirmed they could eventually reproduce it, but not planning to address this issue. It was flagged instead as an enhancement request instead of a bug.
Click Accept as Solution to acknowledge that the answer to your question has been provided.
The button appears next to the replies on topics you’ve started. The member who gave the solution and all future visitors to this topic will appreciate it!
These simple actions take just seconds of your time, but go a long way in showing appreciation for community members and the LIVEcommunity as a whole!
The LIVEcommunity thanks you for your participation!