I'm having same issue. 4G won't connect even with my iPhone next to it and showing 4G available. My router came with newest firmware so maybe try putting an older version on and see hot it works.

Model : Hardware Version : Firmware Version : ISP : Hi all I recently bought a mr6400 as a cure to my rather slow internet problems. I can comfortably get a 4G signal with download speed of 40mb/s...