You have done what cisco document most of the time says, before conclude hardware wrong.
follow below steps (i know you mentioned done reset ) make sure it is the order of operation we do some time small tweaks to work.
1. With the router connected to the power cord (only power cord no Ethernet cable), click the reset button for 30 seconds.
2. After that 30 sec, remove the power cord from the router for another 30 sec, very important keep pressing the reset button always.
3. after that min plug back in the power cord to the router for another 30 sec, ALWAYS holding the reset button.
4. after that minute and a half release the reset button wait for 1 min and do a power cycle, (unplug the power cord from the router for 5 seconds without pressing the reset button and plug back in)