no configuration for longer cable, POE supports 60 mts.and you posted that you try nearly 5 or 6 longer cables and you tested them, if you are sure, the shorter cable is punched exactly as the longer ones, straight not crossed or all of them are bought all ready punched, then its your POE

i have 25 meter wire and its working nicely may be there is fault in some thing recheck and update ur cpe :)

umm thanks guys, I don't have an enterprise standard devices to check the cables. I just using a cheap LAN tester to check for connectivity. With these testers, even if it shows the cables are all OK doens't mean it will check the wires for power transmitted. CPE should be fine as it works fine on shorter cables. and Yes I'm sure I've punched the cable accordingly. I've tried on both ends with 568A and as well as 568B standards. They work well on normal data transfers. and I know well not to use cross over cables in this scenario.
The CPE is a new Out of the box device. All i wanted to do is test on longer wires for now, which failed. My though is also on the way I crimped the cable on the long wires. but I've tried it 5,6 times bothe on cat5e and cat6. It's the same. Only the power light is lit up. No connectivity. I' will try with more new cables and crimping...

and also is there anyway, there would be an issues with the ethernet NIC cards. ??? Will tweaking the NIC's property would help on supplying power on the longer wires and with data transfer ???

thanks

amazing answer, but in my country this is what TP-lLINK answered, if its your poe, TP-LINK does not sale a poe that can replace the original you have to use your warranty