<r>After fiddling with this device for a couple of days I finally got this to work.<br/>
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I am using a SIM card from an AT&T ZTE hotspot so I know the sim and account are good. When I originally got this hooked up and the SIM registered, it worked great with all default settings and I was able to connect to the internet. I even downloaded the latest version from the LTE interface. Big mistake, and I should have noted the version that originally came loaded because 6.42.1 ended up not working. <br/>
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To keep this short and sweet, I knew that it came with 6.40.x, but I was not sure which, so I started rolling back and trying different versions. No luck. Mikrotik suggested making sure the APN was set right, but I tried all that I could find like "phone", "pta", "wap.cingular". Nothing worked until I found an old LTE guide from a Mikrotik conference in 2015: <URL url="https://mum.mikrotik.com/presentations/ ... rian.pdf<e>[/url]</e></URL><br/>
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<B><s></s>"broadband" did the trick for the AT&T APN setting. <e></e></B><br/>
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There is an issue in the latest version of 6.42.1 one though. Not sure if it affects <6.42.1, butt they changed it to where you can't manually set the APN. So what you have to do is roll back to >6.40.3, set the APN, update to the latest and now that option shows up in the list. It seems any APN you set before shows up in that list, but no way to manually enter.</r>

APN configuration is moved to the Interface LTE section - there is a button APN Profiles. There you can create multiple APN profiles and then choose that in the interface lte.

Got it. Thanks!

After updating to 6.41.2 and using the working "broadband" apn, I tried the default APN which uses "internet", and it seems to be working fine on AT&T as well now. Puzzling since this is all default settings.

For AT&T APN's you should use either: broadband, phone