Lets stick with this one for now ,,, as i am pretty sure the connection on that will be different ..
Do me a favour when you detect the modem put some force on the modem pcb pin header by pushing it forward or backwards just want to see if it detects at all ... do this a few times , you just need to keep on hitting f1 on your keyboard to refresh fcusb and whilst doing this see if you can move the pin header ,, maybe one of the pins is not making a good connection.