Hi,
Just trying to guess...
- May be a power supply issue. Sometime, power supply are designed too tight and they may suffer and be spoilt after some time.
- If not, could be a firmware issue (very bad) since the power LED is blinking orange during 10-20s when the router is not faulty.
What F/W (firmware) version do you have on the sticker on the router ?
So, in both, could be that the CPU is stuck on some very early boot up stage...
If it's the case, better ask D-Link for RMA because you will never been able to reach the boot loader page to reflash the firmware.
On my side, my recently updated router gave me an orange blinking WAN LED without any reason.
I just switched off / on the router to "fix" this.
I hope I'm not going to get the same problem that you are facing guys.
Good Luck with D-Link support !

Regards,
HP