Before using software tools, try a "30-30-30" reset to clear the NVRAM: Hold the reset button for while powered on.
For older versions of the R6300, Netgear provided a dedicated software utility on the original Resource CD. Must be run as an Administrator on your PC. Netgear R6300 Firmware Recovery Utility
Manually set your computer’s IP to 192.168.1.10 and Subnet Mask to 255.255.255.0 . Before using software tools, try a "30-30-30" reset