The file is encrypted by EFS and cannot be opened when logging into the original system. Why?

Question

I originally had two hard disks, an SSD and a mechanical hard disk. The files were in the mechanical hard disk. Later, I added a 1T solid state disk and a mechanical hard disk, and installed a new system in the new solid state disk. Then, in order to facilitate classification management, I put the files of the old mechanical hard disk into the new mechanical hard disk. But today, I found that some files could not be opened. When I started up, two systems were displayed, and I could choose to enter. When I entered the original system, I still could not open files. Why? There is a Logo of.