I had some problems running my 32G thumbdrive in the Teclast 98 Pro. But I troubleshooted it to the white USB Adapter that was included with the tablet. After I changed it, my thumbdrives – including thousand of files were read with no problem. I am using a USB 4Port Hub with charger and the thumbdrive concurrently.
So I bet most problems with Thumbdrives reported here were because of the USB adapter. Wiggle the Thumbdrive in the adapter plug and see if it will connect. And it wouldn’t hurt to blow some air in the female USB adapter connector and maybe if required a cotton swab cleaning damp with alcohol.
Tablet in Windows 10 mode is really super.