You should not be prompted to enter any login credentials, when accessing bootloader menu. Make sure you have done the following as described:
- Unplug all cables from the router
- Plug in one Ethernet cable for your computer into any LAN port
- Press and hold the reset button
- While holding the reset button, plug the power cable into the router. After you plug in the power cable, continue holding the button for another 4-8 seconds
- Release the reset button
- All ethernet LEDs will start blinking simultaneously. If that is not the case, repeat the steps again.
- In order to reach the router, you'll have to set up a static IP address that's in the 192.168.1.0/24 network on the device from which you are connected to the router.
- When set your computer's IP, you should be able to reach the router's HTTP server. The address for firmware upgrade is 192.168.1.1/index.html.
Also, could you check if you have SSH access to the device? If you are using a Windows machine, download PuTTy client and try logging using these instructions. If you manage to login successfully, execute command firstboot to reset the router and try default logins again.
Can you confirm that the router itself is working properly, provides internet access to connected devices?
