DAR1682 USB Drive

Anyone know the max size of drive that the DAR1682 "panoramic modem" can handle for sharing? It seems to handle smaller devices like a 128GB but when I try to connect something large enough to handle my required storage for video sharing it doesn't recognize. 1st I was thinking it might be the 128gb stick was a USB3 but I ordered a 4tb USB disk and it also fails. And before someone asks yes I've tried small "disks" instead of SSD sticks and they work. Just trying to figure out the largest I can attach or if maybe I need a firmware update?