I put my Mobley SIM card into this AT&T netgear router Hot spot
AT&T Netgear 815sAnd use the available mimo antenna
Hopefully you have already gone thru the SIM unlock procedure with the Mobley
If not and the needed router gives you a SIM error msg
You might need too tell att you have SIM problems with the Mobley, (not a dead Mobley) and you need a new SIM, then put it in the new hotspot router,
You didn't say how dead, if the Mobley Wi-Fi works but the cellular is dead, you might still access administration and unlock the SIM if you have the puk code, what many of us did was to set our own SIM lock code, so AT&T could not alter any settings to the SIM or the device,
The lock unlock change lock code settings are accessible thru the device administration login url from your web browser,
After the normal wifi connection has been made
Looking ahead to Feb 2022, I jumped on the T-mobile wireless home internet gateway, and plan on replacing my old Samsung S5 Verizon phone, so I can switch to Visible and reduce my current $148 per month vzw bill, to $25, two months savings will cover the cost of the replacement phone, after that I will still be saving $$70 every month, even with having the new T-Mobile account,
I can explain it to you.
But I Can Not understand it for you !
....
Connected using T-Mobile Home internet and Visible Phone service
1997 F53 Bounder 36s