There is an odd problem during using ocserv

[z jl]

Hello,
There is an odd problem during using ocserv: After build my VPS on ocserv, all my clients are connected very well like Windows client (Anyconnect), BlackBerry (Anyconnect), IOS(Anyconnect), Android(Openconnect), but only Android client (Anyconnect) is failed to connect.
Android client error 
                 The VPN client agent SSL engine encountered an error . 
Server version:           centos7
Linux kernel:         Linux My 3.10.0-327.28.3.el7.x86_64 #1 SMP Thu Aug 18 19:05:49 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
Ocserv version:    ocserv 0.11.8
Gnutls version:     3.3.24
Ocserv config:           

auth = "plain[/etc/ocserv/ocpasswd]"
tcp-port = 443
udp-port = 443
run-as-user = ocserv
run-as-group = ocserv
socket-file = ocserv.sock
chroot-dir = /var/lib/ocserv
isolate-workers = true
max-clients = 100
max-same-clients = 0
keepalive = 32400
dpd = 90
mobile-dpd = 1800
switch-to-tcp-timeout = 300
try-mtu-discovery = false
server-cert = /etc/ssl/certs/server-cert.pem
server-key = /etc/ssl/private/server-key.pem
compression = true
no-compress-limit = 256
tls-priorities = "NORMAL:%SERVER_PRECEDENCE:%COMPAT:-VERS-SSL3.0"
auth-timeout = 240
min-reauth-time = 300
ban-reset-time = 300
cookie-timeout = 86400
persistent-cookies = true
deny-roaming = false
rekey-time = 172800
rekey-method = ssl
use-utmp = true
use-occtl = true
pid-file = /var/run/ocserv.pid
device = vpns
predictable-ips = true
ipv4-network = 10.12.0.0
ipv4-netmask = 255.255.255.0
dns = 8.8.8.8
dns = 4.2.2.1
ping-leases = false
cisco-client-compat = true
#dtls-psk = false
dtls-legacy = true


Hope you can offer solution soon, thank you.