hi i am from iraq i have router board 433 it was work very well in 5 meter of fstp cat5 through PoE but it is not work in 10 meter in same cable

Does the RB433 starts up when using 10m cable? Please describe power supply and PoE adapter that you are using.

hi
i am used the 24V 0.8A Power Supply from mikrotik
yes the RB433 starts up when using 10m cable

So how does the router powered through 10m cable work differently?

hi and good day
when i connect this router through 5 meter of cable i can see it in winbox ok
but when i connect it through 10 meter of cable i cant see it in winbox but the router starts up and the blue led is on with beep then beep beep
when i start the winbox the winbox don't see the router
only the winbox see this router in 5 mater of cable
note sorry for my English Language

Does that happen with any 10m cable or did you try it with only one particular 10m cable? Thanks.

that happen with any 10m cable

Do you have any other routerboard that you can use to rule out a potential cable fault?

You could do some tests with a poe injector on each ethernet port in order to troubleshoot your equipment. Try to make your own network cable and of different length, e.g. 7m or 12m. If none of it helps you can contact support or RMA the device. Just make sure that you troubleshoot the device correctly.

Feel free to ask if you'll need more tips.