AT&T Beam (AC340U) not working

Has that setup ever worked? That device is a USB modem primarily intended to provide cellular internet connectivity to a laptop. I’m not seeing any information about plugging it in to a Cisco router. Does the Cisco recognize the device? You obviously also need an active SIM card and data plan. 

It's 8 years old, at least.  I would think it's no longer compliant.

When was it last working? 

On what wireless plan?

It has been setup for three years. And worked last year once primary internet service was down.

When last year?

And on what plan?

AT&t's 3G shut off has affected a lot of devices. That device does not appear on the list of devices that are still supported.

And AT&t has discontinued some prepaid plans without grandfathering them. 

That device does not appear on the list of devices that are still supported.

I had to google that device to determine what it is but didn’t realize it was so old. It’s supposed to be LTE capable but if it’s not on the supported list, that’s probably the reason. It’s also very possible whatever plan it was on was discontinued or just no longer works, especially if it was a data connect plan.