Hi All,
I ordered two SXT LTE modems for my customers. The first one workes just fine, when I insert the SIM card and find direction it works. I have a problem with the second one. Same position and the same SIM card and there is no signal. I need Your help to find the solution.
Please upgrade RouterOS to the latest long-term version.
Have you opened up the sxt as it looks like the antenna cables are not attached.
Quite some improvements have been done for LTE devices, especially as of 7.2rc5.
I have an SXT LTE6 running that version and have no problems whatsoever.
If the device is under warranty, I suggest to first check with the vendor if you will not loose warranty when opening the device.
Maybe best to request replacement.
I would second this, I know at least with the sq units that the case is ‘plastic welded’ together so you would have a hard time getting the case back together again if this is the case with the LTE 6 models.
I third this! 
On a serious note though, there is not enough information to diagnose this as the antennas being disconnected.
Opening the case should be a last resort when the most sensible causes have been eliminated.