Can you explain revokaction keys from doc (not revocation certificates)?

hi. i’m struggling with this piece of text

especially part about " Check certificate authenticity"

particularly “the key had not expired or been revoked when the transaction occurred.”

what does it mean? which key was not expired or revoked?
Am I wrong that key is private key from issuers bitcoin address? if so, how can it be expired or revoked.
If not, what key is meant here?

if its not private key from bitcoin address, then what kind of key is it and where is it published and where its expiration and revokation details are published?

i’m totally puzzled with this piece of information and will highly appreciate any help or clarification.

Thanks in advance

I think you are confusing two different pieces of information. “Checking certificate authenticity” is about checking the issuer’s keys. Separate from that, an issuer profile may contain a list of revoked certificates (which doesn’t require/use expiring keys themselves in any way).