If the error "VERIFY ERROR: depth=0, error=CRL has expired" is received when a client attempts to connect to the OpenVPN server, it can be fixed as follows:
cd /etc/openvpn/easy-rsa
easyrsa gen-crl
Should result in:
[root@vpnserver easy-rsa]# easyrsa gen-crl
Using SSL: openssl OpenSSL 1.1.1m 14 Dec 2021
Using configuration from /etc/openvpn/easy-rsa/pki/easy-rsa-390.asdf/tmp.qwer
An updated CRL has been created.
CRL file: /etc/openvpn/easy-rsa/pki/crl.pem
It should now be able to connect again.
However, how do you generate a CRL that has a longer expiration, like several years?