@Sunshine Yes, if I restart the modem(both software and hardware reboot) it again connects to 4g+. But it doesn't stays in 4g+. I did checked with my mobile(both iPhone and Android) it always stays...

I bought MR600 few weeks ago. I'm using Airtel simcard which supports 4g+. I also installed beta firmware to manually select frequency bands(in my case band 3, 40). When I hit save it connects to 4g+...