PPP with HL6

I am trying to implement the PPPoS from picotcp on HL6.

I have code working perfectly on SL6087 that works like:

ATZ
OK

ATE0
OK

AT+CREG=1
OK

AT+CGREG=1
OK

AT+CGDCONT=1,“IP”,“internet.proximus.be”,
OK

AT+CGATT=1
OK

ATD99**1#

CONNECT 38400

PPP: Modem connected to peer.
Sending LCP CONF REQ

Received LCP CONF ACK
Optflags: 0182
Sending LCP CONF REQ
Received LCP CONF ACK
Optflags: 0182
Received LCP CONF REQ
Setting AUTH to c023
Sending LCP CONF ACK
PPP: LCP up.
PAP: Sending authentication request.
PAP: Received Authentication OK!
PPP: Authenticated.
Sending IPCP CONF REQ, ipcp size = 34
Received IPCP CONF REQ
Sending IPCP CONF ACK
Received IPCP CONF REJ
Sending IPCP CONF REQ, ipcp size = 22
Received IPCP CONF NAK
Sending IPCP CONF REQ, ipcp size = 22
Received IPCP CONF ACK
PPP: IPCP up.
Received IP config 46.179.146.96
Received DNS: 80.201.237.239
Assigned ipv4 46.179.146.96 to device ppp0
setsockopt: Nagle algorithm disabled.
Launching PicoTCP echo server

When I try the exact same code, with exactly the same SIM card, on HL6 the negotation never gets passed LCP. And I just get:

Sending LCP CONF REQ
Received LCP CONF REJ
Sending LCP CONF REQ
Received LCP CONF REJ

What might be different on HL6 so that this doesn’t work on the HL6 modules?

Are you able to see what the options in the configure reject message are?

Regards

Matt