Hi! I am encountering the same issue! I have replaced the # defined for the modem from TINY_GSM_MODEM_A7670 to TINY_GSM_MODEM_SIM7600, which got the sketch to compile, but the modem doesn't get any GPS reading. This post is the number one result on Google, but sadly, there isn't much help here yet. As you've pointed out, I have a feeling it's a TinyGSM library issue, but I am kinda lost on debugging it from here. It'd be great if someone got the GPS working and found this post sometime in the future...