MR2100 USBC Tethering only auto off after inactivity

MR2100

NTGX24_10.17.10.00

Big Sur

MAC

1.This unit works well when on WiFi

2. When on USBC Tether only there is a complication

3.In USB Tethering option Select USB Tether Only

4. When plugged into MAC 2021, after reset the unit works as described in literature

5. If left alone with no activity inputs the unit disconnects from the MAC

6. Reset is repetative, multiple DHCP refresh, cable unplug,replug

Question

What is the setting I am missing that is resulting in the tethered unit auto disconecting from the MAC ( or vica versa).

Is it a NIGHTHAWK setting or am I missing an obvious MAC setting.

Thankyou in advance for any advice. The specialist retailer who is also the branded seller of this unit, and is the largest network provider in the country, wasnt able to help at local level after 2 shots at it.

regards Peter