Ubuntu 26.04 + HP Probook 640G8 + Fibocom L850-GL / Intel XMM7360 + t-mobile = no data transferred but connected

this is driving me crazy... and so I need some help please. I have several hp probook 640g8 with fibucom L850-GL modem (= intel XMM7360). I want to use them with Ubuntu 26.04 lts desktop. On the fist notebook everything runs fine - insert sim card and lte-connection can be used. On the other notebooks this doesn't work. The Modem seems to be connected ( mmcli -m any > Status : state : connected).…