I'm unable to get to an older fw; tried both, the restore app and the cfe method.
You may have already tried this.
Static IP on TCP/IPv4 of adapter.
IP 192.168.1.2
subnet 255.255.255.0
gateway 192.168.1.1
Make sure no USB devices are connected.
Push reset button until power light starts blinking.
Let router completely reboot without touching anything.
Once router is back up, turn off the power button then hold in reset while powering back on to get into recovery mode.
Launch browser to 192.168.1.1
upload firmware and wait wait wait