The sim card sent was tested in office and confirmed working and performing to normal speeds prior to packaging it up and shipping it your way.

Be advised that while changing the sim card itself is relatively simple, Netgear model devices now require an extra few steps prior to service being restored once you've changed the sim card, as I'm sure you've already figured out. We have implemented an enterprise level VPN on your connection between the AT&T network and your device, and in order to get your device into that "blanket" so to speak, you'll need to manually add an APN profile and then select that APN profile you've created in order to get access to the AT&T network by running thru Olive IP Network via that VPN using the custom APN profile created. 

Most users report the need to log into the MR1100 User Interface AFTER installing the sim card and rebooting the device, in order to hit a "Submit" Button for the broadband/ AT&T carrier network which is located on an APN verification pop-up window. This pop-up window should appear once you enter the device's sign-in password (located on the label of the device if you've done a factory reset of the device). You will then need to manually setup the APN. The name doesn't really matter but we recommend putting AT&T. The APN is "broadband" by default with generic AT&T data plans such as our Blue Basic or Blue Premier Plan. You'd need to manually setup your APN profile if your on a custom AT&T data plan such as our Blue 300 or Blue 450 plans. Keep reading below for further guidance on any plan as those plan specific APN settings are listed below. 

This can be done using a phone connected to your wifi by typing in the following IP: to your phones web browser's URL bar. It can also be done using the Netgear Mobile App. If you are using a computer, just open a web browser and type in the IP address (listed above) into your URL bar on your favorite web browser. The Netgear MR1100 display page also tells you a log-in hyperlink that can be used instead of the direct IP address. Either method works the same, and both methods require your phone/ tablet to be connected to the Netgear mobile router's WIFI (which is listed on the display screen of your device).

****Follow the below step CAREFULLY to ensure proper provisioning of the sim card on the network! Failure to follow and setup your APN correctly, likely we result in line termination and or throttled speeds for the duration of the service cycle. ****

Sim Card, label and reset button locations (for your reference. Information is different on your specific device). 

After sim card change (display screen after one tap on power button) (Blinking Amber light on device indicates setup required) - 

After Logging into the device (APN pop-up window). This page only appears IF you have not done a factory reset of your device. (If you have factory reset your device, you will get a password change and wifi change setup screen before the APN screen). Hit the Submit button on this page

Next you will get the below (APN setup Page). Ignore what is in the picture below and type in the following for the custom APN setting profile dependent on the Olive IP subscription you are using (IF YOU ARE UNSURE OF THE PLAN OR APN INFORMATION REQUIRED PLEASE CONTACT OUR TEAM PRIOR TO USING THIS NEW SIM CARD):

Blue Basic Plan:
APN name: AT&T Regular
APN: broadband
PDP Roaming: None
Authentication - None
Username-leave blank
Password: leave blank

Click on ADD once you've entered/ selected the appropriate settings.

Next you will see the Cellular setup page. Select the box next to Data. Ensure LTE All is showing under Band Region. You should see AT&T under Network selection and the "Active bubble" next to your created Custom APN profile should be filled in. (will look different than the below picture IF your not on the default/ regular AT&T APN).  Hit Apply as the final step.

This will complete your APN setup. Be sure to continue on and do the other recommended setup steps (Link below)  if you've not configured your device already or have a setup you like to use. A Reboot of your device may be required depending on the firmware you've got on it.  

See below added resources:
Netgear MR1100 - Setup Guide
Netgear MR1100/M1 Nighthawk Troubleshooting
MR1100 - APN Setup