MX Devices and internal SIM Card Issue

[erhanevgin]

Hello Team.

We have great trouble with Meraki MX67C.

We are using MX67C  for our SD_WAN project.  But however, some MX67C devices are not working with the internal SIM cards properly.  You can see the details below.

We are using the same operator sim cards for all devices. what could be the problem

regards. 

We will use SIM cards just for redundancy.

[ww]

Could be Bad reception.

Are they located in a open space, or in a 19inch rack

[BlakeRichardson]

Thats a really good point, a rack will act like a faraday cage. 

[erhanevgin]

Devices working in open area. Besides we are using the same SIM card with the telephone same location and it's working properly. 

[Fady]

Are you using MX18 firmware?

[erhanevgin]

Current version: MX 18.107

[Fady]

Can you drop to MX17 and try again

[erhanevgin]

We have tried all older firmware versions. problem still continues