I started to get this error today. I't was working without any problems to this day. But today I've lost connection and had to reboot whole device to make it work again.
I have network connection to ISP but in "Cellular" tab of lte1 interface i've got:

IMSI: +CME ERROR: 100

Poland/Orange network.

[admin@MikroTik] > /interface lte info lte1 once
pin-status: no password required
functionality: full
registration-status: registered
manufacturer: "MikroTik"
model: "R11e-LTE"
revision: "MikroTik_CP_2.160.000_v008"
current-operator: Orange
lac: 52901
current-cellid: 328302xx
enb-id: 1282xx
sector-id: 2xx
phy-cellid: 4xx
access-technology: Evolved 3G (LTE)
session-uptime: 16m22s
imsi: +CME ERROR: 100
subscriber-number: +CME ERROR: 100

I guess it can be related to network operator. I'm using it in passthrough mode with public IP.

Restarted device 2 times and it works ok now....

No, 2 times restart no help =(

/interface lte firmware lte upgrade=yes
This command helps me.

But i used another sim-card without login+pass auth

LTE with Auth began work only after upgrade.