After turning Wireless Mode off under 192.168.2.1/index.htm (aka router admin page) for both 2.4GHz and 5Ghz, I was unable to access the same admin page with a wired connection.
Tried harware reset, factor-default link, reflashing the firmware file and several times, but no luck.
Bought another refurbished router and noticed that it´s model was slightly different F9K1109 URL - decided to flash it´s binary to F9K1103v1 and it worked!
Click source link below for the firmware of Belkin N750 F9K1109v1
Do not jump to this solution directly - give it a try after you have tried everything and just before making Belkin N750 F9K1103v1 part of landfill.
Regarding reflashing the firmware, download the binary file from the source link provided below, login to your Belkin N750 F9K1103v1 router admin page and click the "Firmware Update" link, then "Choose File" and finally click the Update button.