MC7700 AT&T LTE: PPP/DUN over USB interface 4 not working

I have an MC7700 configured for DirectIP (PID 68A3). I am developing in a proprietary embedded environment with no OS.

If I use an AT&T SIM that does not allow LTE access (modem reports CNTI: 0,HSDPA/HSUPA ) then I can use ATD99***1# with a PPP driver over USB interface #4. PPP works fine and I can upload / download fine, albeit at HSPA speeds.

If I swap to an LTE capable SIM card then there is no response to the ATD99**1# on interface #4. If I connect the modem to a PC and run watcher I get internet access at the higher LTE speeds.

I am wondering whether the MC7700 only allows DirectIP for user data when the modem is registered on the LTE network ? If so is there any way to override this to allow PPP to be used on LTE because I don’t currently have a Direct IP driver (though I may write one in the future).

Can you try changing the PID to 68C3 and check PPP connection over LTE?