Modem mode is where the hub doesn't act as a router, and you connect your own router to the hub. You'd know if you've set it to modem mode.
Next stop, try a pinhole reset (you'll need the settings password on the base of the hub, don't confuse it with the wifi password also on the base).
If the LED's still red after that, the forum staff will need to book you a technician visit to check it out and most likely replace it.