Hello!
The error here is different. OpenSSL 3 doesn't accept certificates signed through SHA1. Since 2017 we have been signing client certificates with SHA512 and you have a pair generated in 2016. We don't force the renewal to avoid sudden and unexpected disconnections to our unaware users. Thank you, you're a long time customer indeed!
Please:
log your AirVPN account in to the web site
click "Client Area" from the upper menu
click the "Devices" button
click your client/key pair "Details" button
click "Renew"
from Eddie main window uncheck "Remember me", log your account out and then in again (you will have to re-enter your AirVPN account credentials) and the problem will get resolved. (*)
(*) If you don't run Eddie, from the Configuration Generator generate new configuration files for the software you run to connect to AirVPN.
Detailed instructions here: https://airvpn.org/forums/topic/26209-how-to-manage-client-certificatekey-pairs/
Kind regards