If the LED does not light up at all, it is not a good sign. You can try different power wall outlets and/or different power supplies. Different ethernet cables as well. Also connect it to a PC/laptop directly to see if there are any LED changes. Also check back LEDs, check manual for what different colors mean for front and back LEDs.
If there are LEDs on the back, there is a slim chance the LED got burned. If you were set to DHCP, power it up and check your DHCP server lease table (usually this is your router) to see if it is listed. If it is not, not good at all. Complete unit might be dead.
If not clear on what DHCP is or how it works, google and also read your router manual.
If you do determined the unit is dead, you can try to recover the files using this guide:
And for the future, always keep 2+ copies of important files on different media aka backups. This one is easy to read/understand: Digital storage basics, Part 3: Backup vs. redundancy - CNET
