Uploading of PDF and video files on Rachel Plus issue

I am trying to upload PDF files and videos from a USB stick to the Rachel Library but it seems to loading forever.

I logged in using the teacher’s account and have appropriately created a category for my uploads.

Do you have any idea of what could be the cause? Am I missing something? I did everything according to your tutorials and instructions given but seems to be loading forever but not copying it into the device storage. USB is plugged on the USB port of Rachel plus device.