I've noticed that Thingy:91 USB code has some issues related to proper handling attach/detach events resulting in incorrect response to usb host requests. Windows device manager states that "A request for the USB device descriptor failed."
It happened several times already and the only solution is to power off/on device.
Device is updated with thingy91_ltem_dfu_2019-11-29_d3130d77.hex
AT%HWVERSION: E244