I have the U301 and the Sprint 300s router and the latest firmware does not seem they are compatible. Any news on a new firmware version for that unit or a 4G upgrade for their CTR350?
Here is the product site from the maker
if you don't see what you are looking for then i would check the Live Chat option on the right side.
Sprint S.M.A.R.T AgentsSprint S.M.A.R.T Agent are here to help Monday through Friday 6:00 AM CT - 6:00 PM CT. If you need to speak to an agent outside of these hours, please visit Sprint Chat