Identify Protocol, but device is invisible

Hi,
i am fighting a the moment with a GT 02 Clone (GT02-MT6261D_V2.0).
Did the steps for "Chinese Clones", sending the "fix060s..." and tried ports5001,5002...5093...
I am sure that I sent correct APN and server IP.
Than I tried steps for "Identify Protocol".....
In both situations the device wasn´t listed in the tracker-server.log

For checking all,
I took another good running device (no GT02) and changed the port from 5009 (this is the correct port) to 9999.
I expected to see this device in tracker-server log marked with a warning,
but this device wasn´t listed,too.
I change to the correct port, than the device is listed in log file and shown in the map again.

So where is my mistake,
are my thoughts wrong?
Any help requested.

Regards
M.

Check this guide:

https://www.traccar.org/troubleshooting/

Hi Anton,
I just did it,
it seems it is firewall problem of the server......
brrrr,
I didnot notice it, am sorry !
Regards
M.