Hello and thank you for your reply.
I just solved my problem; the AirVPN server list wasn't up to date, so I updated my Gluetun client, and now the Taiyangshou server is working.
However, SERVER_NAMES is indeed plural, as indicated in the Gluetun configuration.
https://github.com/wolffcatskyy/gluetun-airvpn-edition