I recently purchased the Arlo GO Wireless/SIM card activated camera. I was having difficulties with AT&T connection trying to get a sim card activated (you will need an AT&T company sim card) and working with the Arlo app and to "connect new device" So I contacted AT&T and found that you need to adjust the APN location for which the Arlo camera brings in connection to the internet. Here is the link for anyone going through the same issue I did it is " ........ https://www.att.com/esupport/article.html#!/wireless/KB424489?source=redirect
that will help you find the details you're looking for but for anyone using APN the wireless address should be ............. http://mmsc.mobile.att.net
Sorry everyone I forgot to input the model # I was referencing in my post. It is Model #VML4030-200NAS. It definitely worked with my AT&T network (maybe it's not the model that is suppose to be for AT&T, oops 😉 ). Unfortunately I can not speak for any other models within the Arlo GO family.