If Raspberry Pi, OS has to be Ubuntu 20.04 LTS.
Instructions: https://openvpn.net/vpn-server-resources/install-openvpn-access-server-on-raspberry-pi/
Status of Access Server
sudo systemctl status openvpnas
Update host's privkey to OpenVPS
sudo /usr/local/openvpn_as/scripts/sacli --key "cs.priv_key" --value_file "/etc/letsencrypt/live/truhponen.duckdns.org/privkey.pem" ConfigPut
Update host's fullchain to OpenVPS
sudo /usr/local/openvpn_as/scripts/sacli --key "cs.cert" --value_file "/etc/letsencrypt/live/truhponen.duckdns.org/fullchain.pem" ConfigPut
Restart Access Server
sudo /usr/local/openvpn_as/scripts/sacli start
OR
sudo systemctl restart openvpnas