I have the exact same problem with my new GL-MT300A.

  • Reset button does absolutely nothing, holding it for 3 seconds or 10 seconds ( according to the manual) , nada…

  • It doesn’t provide an IP address over DHCP on the LAN port

  • It doesn’t broadcast anything on WiFi.

Completely dead, except it does pass-through WAN-LAN, but that doesn’t help me much.

Since factory reset doesn’t work, how do I a firmware flash/update when I don’t have access to it?

Can it be done with a USB stick?