LM1200 drops but T-Mobile SIM is online

I have same/similar issue. Took verizon sim from jetpack mifi and put in LM1200. Works great when LAN to laptop. Connected LAN to Internet port (yellow) on X6s AC4000 Nighthawk Netgear tri band wireless router. It worked for a hot minute with laptop and ethernet tv but wireless stuff never connected as the LAN link kept dropping. What gives?? Worked flawlessly overnight when connected to one thing but the minute i connected to wireless router, it drops connection.

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TexMark wrote:

LM1200-100NAS

Updated firmware upon initial boot up on 11/21/21

T-Mobile 4G LTE SIM with 50GB plan

 

My new LM1200 has a T-Mobile 4G LTE SIM on a 50GB plan. It connects to a Nighthawk AC1750 router and I have 5 security cameras, a weahter station, remote lighting controls, and a Mocreo sensor hub all connected at the marina boat dock. I spent hours on the phone with T-Mobile the past few days and they ruled out everything on their end. I can reboot it to get it online for a day, then it drops and the only fix is to unplug and restart it. It statys connected a few hours to a day and drops again. I updated the firmware two weeks ago when I purchased it and tried factory reset twice. Same thing. It's a huge pain because the boat dock is 60 miles away and I monitor it at home using the Netgear modem to reach the devices. I have to drive up there to reboot it. I tried talking to technical support and the experience was beyond horrible. I have never experienced such horrible customer service in my life. It took 15 minutes just to get my identity established (email, phone number, product serial number). I was put on hold, passed to someone else and the same questions over and over. After 30 minutes of getting no where even near troubleshooting, I told them to forget it and hung up. Netgear, your technical customer support is horrible - beyond horrible. I am at my whits end after spending hundreds of dollars on the modem/router pair that is supposed to be certified for T-Mobile service. What can you do for me? Has anyone else been through this or currently going throug this? Thanks in advance.

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For this disconnection issue, please enable Keepalive timer and leave the timer setting as the default value. This has been confirmed by other T-Mo customers that the setting will work. Some carrier's network will disconnect the data link if there is not active data transfer for a certain period of time. Enabling Keepalive timer will prevent the issue from happening.

Please let me know wehther this helps.

Regards