Gabb Phone Z2 not prompting me for USB file transfer

I always use my Gabb Phone Z2 for transferring videos to watch on road trips, but it's different now. I was about to transfer some episodes to my phone, and it always prompted me to choose either file transfer or charging only. But 3 days ago, I didn't get that prompt. It only started charging, and file transfer did not work. I restarted my phone, the computer, and factory reset my phone but still nothing. Is this a system or phone issue, or is it related to my charger or something else?