Knock suddenly not working in syn mode with nc -z command

[osevan]

Since one month with debian siduction, knockd cant comes to open stage 2 and 3

Only open stage 1 and timeout after 10s like declared in config file.

Thanks and

Best regards

[osevan]

Dec 04 17:07:22 8 knockd[3674070]: MYIP: openSSH: Stage 1
Dec 04 17:07:22 8 knockd[3674070]: MYIP: openSSH: sequence timeout (stage 1)
Dec 04 17:06:39 8 knockd[3674070]: MYIP: openSSH: Stage 1
Dec 04 17:06:38 8 knockd[3674070]: MYIP: openSSH: sequence timeout (stage 1)
Dec 04 17:06:21 8 knockd[3674070]: MYIP: openSSH: Stage 1
Dec 04 17:06:21 8 knockd[3674070]: MYIP: openSSH: sequence timeout (stage 1)
Dec 04 17:05:28 8 knockd[3674070]: MYIP: openSSH: Stage 1
Dec 04 17:05:28 8 knockd[3674070]: MYIP: openSSH: sequence timeout (stage 1)
Dec 04 17:04:34 8 knockd[3674070]: MYIP: openSSH: Stage 1
Dec 04 17:04:34 8 knockd[3674070]: MYIP: openSSH: sequence timeout (stage 1)
Dec 04 17:04:02 8 knockd[3674070]: MYIP: openSSH: Stage 1

[osevan]

/etc/knockd.conf
[options]
UseSyslog

[openSSH]
sequence = myport1,myport2,mypor3
seq_timeout = 10
command = mycommand
tcpflags = syn

[osevan]

cat /etc/default/knockd

control if we start knockd at init or not

1 = start

anything else = don't start

PLEASE EDIT /etc/knockd.conf BEFORE ENABLING

START_KNOCKD=1

command line options

KNOCKD_OPTS="-i eth0"