Check your System Log for the error message. Chances are you are trying to start two servers with the same IP range.
First 10.8.x.x , Second 10.16.x.x
Log:
May 18 19:05:53 rc_service: httpd 484:notify_rc restart_chpass;restart_vpnserver2
May 18 19:05:55 kernel: ADDRCONF(NETDEV_UP): tun22: link is not ready
May 18 19:05:55 kernel: device tun22 entered promiscuous mode
May 18 19:05:56 openvpn[8266]: WARNING: POTENTIALLY DANGEROUS OPTION --verify-client-cert none|optional (or --client-cert-not-required) may accept clients which do not present a certificate
May 18 19:05:56 openvpn[8266]: OpenVPN 2.4.2 arm-unknown-linux-gnu [SSL (OpenSSL)] [LZO] [LZ4] [EPOLL] [MH/PKTINFO] [AEAD] built on May 12 2017
May 18 19:05:56 openvpn[8266]: library versions: OpenSSL 1.0.2k 26 Jan 2017, LZO 2.08
May 18 19:05:56 openvpn[8267]: PLUGIN_INIT: POST /usr/lib/openvpn-plugin-auth-pam.so '[/usr/lib/openvpn-plugin-auth-pam.so] [openvpn]' intercepted=PLUGIN_AUTH_USER_PASS_VERIFY
May 18 19:05:56 openvpn[8267]: Diffie-Hellman initialized with 2048 bit key
May 18 19:05:56 openvpn[8267]: TUN/TAP device tun22 opened
May 18 19:05:56 openvpn[8267]: TUN/TAP TX queue length set to 100
May 18 19:05:56 openvpn[8267]: do_ifconfig, tt->did_ifconfig_ipv6_setup=0
May 18 19:05:56 openvpn[8267]: /usr/sbin/ip link set dev tun22 up mtu 1500
May 18 19:05:56 kernel: ADDRCONF(NETDEV_CHANGE): tun22: link becomes ready
May 18 19:05:56 openvpn[8267]: /usr/sbin/ip addr add dev tun22 10.16.0.1/24 broadcast 10.16.0.255
May 18 19:05:56 openvpn[8267]: Could not determine IPv4/IPv6 protocol. Using AF_INET6
May 18 19:05:56 openvpn[8267]: Socket Buffers: R=[122880->122880] S=[122880->122880]
May 18 19:05:56 openvpn[8267]: setsockopt(IPV6_V6ONLY=0)
May 18 19:05:56 openvpn[8267]: TCP/UDP: Socket bind failed on local address [AF_INET6][undef]:1194: Address already in use
May 18 19:05:56 openvpn[8267]: Exiting due to fatal error
May 18 19:05:56 openvpn[8267]: Closing TUN/TAP interface
May 18 19:05:56 openvpn[8267]: /usr/sbin/ip addr del dev tun22 10.16.0.1/24