Hello everyone!
I have the Beryl AX and a ZTE MF79U. I configured USB tethering for the ZTE and it works just fine. But after a certain amount of time the Internet disconnects and i have to put the PIN for the SIM Card back into the ZTE Webinterface.
I did not find any information regarding this Problem searching the web and hope that some of you had the same issue and could solve it.
Looking forward to your answers! 
Hello,
Does the SIM card you are using on ZTE modem have set a PIN code?
If it is set manually, you can remove or close the PIN code.
If ZTE does not support this setting, you can insert the SIM card into your phone, then find the relevant settings, turn off the PIN code, and insert it to the ZTE modem again, I assume there is no need to repeatedly enter the PIN code.
This problem may be caused by poor contact between the SIM card slot, and it is rereading the SIM card. Rereading the SIM card may require entering the PIN code.
Hello Bruce,
Thank you for your reply!
The SIM Card has a set Pin by the carrier. It is also from a friend so i wont fiddle with the code yet. But thank you for the tip, i may try when he is back on site.
I actually think that it could be bad contact because the ZTE Modem requires a micro sim and i put a Nano sim in there 
It also worked now for some extended amount of time, so I'll try to find the adapter from nano to micro.
Kind Regards,
Klaas