found one her, but not sure if it is the one you need. http://www.tp-link.com/nl-be/download/TL-WR1043ND_V3.html#Firmware

do you want to connect synology nas via usb cable or wireless to the C2600? for wireless, you need to pick up your Wi-Fi on the settings of C2600 and input your password. Then you can find nas under...

see here, http://www.tp-link.com/us/faq-468.html if no luck, you can look for powerline adapters. One goes to router and the other Wi-Fi one upstairs to send signal. Make sure they are in the same...

try reset first and if that doesn't fix, ask the shop or TP-link to provide you a replacement. it seems that this router is not working after firmware upgrade. By the way, do you have dell laptop...

do you want to use it as range extender or wireless access point? can't get started, do you mean no light at all? have you login its setup page?

how do you connect them? A topology may help us to understand the issue here.