I managed to make gpg4win work with openpgp keyserver by reading this article: www.stephenwagner.com/2021/09/30/sophos-dst-root-ca-x3-expiration-problems-fix/
And this tutorial on how to install certificates to Windows10/7: techglimpse.com/dst-root-ca-x3-expired-certificate-error
Apparently, it is because openpgp's certificate also relies on the expired (on Sept 2021) "DST Root CA X3" certificate which older versions of Windows 10/8/7 still use.
(I downloaded the der certificates from letsencrypt instead of the provided links, also needed a restart)
But since using other servers should work, just use that "easy method" instead.
Topic: PGP verification of Bitcoin core download (Read 125 times)
Both keys.openpgp and keyserver.ubuntu are working normally for me. Also pgp.mit.edu, which is the other server I sometimes use. All three are processing Luke Dashjr's key normally without any errors.
For the expired error that OP is receiving - I would first check that your system date and time is accurate, and then I would update Kleopatra/Gpg4win to the latest version, and see if that helps.
For the expired error that OP is receiving - I would first check that your system date and time is accurate, and then I would update Kleopatra/Gpg4win to the latest version, and see if that helps.
Key server mentioned by @Edwardard works on my end. But using keys.openpgp.org show this error message for few times before gpg manage to import the key.
On a side note, both Luke Jr key and openpgp.org TLS certificate is created some time ago so i don't understand how OP see error message "keyserver receive failed: Certificate expired".
Code:
$ gpg --keyserver hkps://keys.openpgp.org --recv-keys E463A93F5F3117EEDE6C7316BD02942421F4889F
gpg: keyserver receive failed: Server indicated a failure
On a side note, both Luke Jr key and openpgp.org TLS certificate is created some time ago so i don't understand how OP see error message "keyserver receive failed: Certificate expired".
It seems the error says Certificate expired if this error came from Kleopatra would you mind to try to refresh the expired keys using this command below.
And make sure that you follow the guide from Bitcoincore.org instead of bitcoin.org
And also try not to use hkps:// you must replace it with hkp://
If it didn't work try other suggestion from this post below.
- https://bitcointalksearch.org/topic/m.60777226
Code:
gpg --keyserver hkps://keys.openpgp.org --refresh-keys
And make sure that you follow the guide from Bitcoincore.org instead of bitcoin.org
And also try not to use hkps:// you must replace it with hkp://
If it didn't work try other suggestion from this post below.
- https://bitcointalksearch.org/topic/m.60777226
I keep on getting "keyserver receive failed: Certificate expired" message, which surely can't be right, what am I doing wrong here. 
Try changing the keyserver, use this one: Code:
gpg.exe --keyserver hkp://keyserver.ubuntu.com --recv-keys E463A93F5F3117EEDE6C7316BD02942421F4889F
So trying to verify 24.0 but using Kleopatra I keep getting a "signatures could not be verified" message. I am guessing this is because I need at least one of the builder keys from the github key list. But when I try to import one of them using this
gpg.exe --keyserver hkps://keys.openpgp.org --recv-keys E463A93F5F3117EEDE6C7316BD02942421F4889F
I keep on getting "keyserver receive failed: Certificate expired" message, which surely can't be right, what am I doing wrong here.
gpg.exe --keyserver hkps://keys.openpgp.org --recv-keys E463A93F5F3117EEDE6C7316BD02942421F4889F
I keep on getting "keyserver receive failed: Certificate expired" message, which surely can't be right, what am I doing wrong here.
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