There are too many softwares installed on disk 1.c, resulting in insufficient space for storing the index files of the contents of disk D in disk C, and the synchronization cannot be completed;

2. The computer power supply is insufficient or the usb extension cable is connected to the dock, so the synchronization cannot be completed;

3. When using the computer, the normal running environment of itunes was accidentally affected, or the itunes Windows usb device management bug displayed in the online data made it impossible to complete synchronization.

Solution: Delete an extra font in the C drive system, leaving a space of 23M (even after deletion, it is still in normal use at present, and the utilization rate of C drive is 85%), then directly connect the dock to the usb interface on the motherboard, and finally take out my idle 128mu drive, insert it into the computer when the itunes synchronization progress bar stops, then safely delete it and reactivate the synchronization progress bar until the synchronization is completed successfully. (It seems that when synchronizing hundreds of m video files, the progress bar is easily stuck many times. )

I hope I can help you!