Cannot decrypt files when copying them to another location

On my PC's HDD I have some files encrypted. Used "folder encryption" that is
in one of folder properties selected "Encrypt data..."

Folder is shown in green in explorer respectively.

In the beginning, when I copied any files from this folder to another
location (e.g. USB HDD) files became automatically decrypted, i.e. I could
read those files from USB HDD on any other PC.

But now something changed. Though I did not make any changes to security or
file system settings, files copied from encrypted folder to USB HDD stay
encrypted. That is - I can read them only on PC where I copied them to USB
HDD. On other PCs where I connect USB HDD files are not accessible.

How can I change it back? I need files copied from encrypted folder to USB
HDD to decrypt automatically, because it's backup procedure and I need them
accessible on any other PC. How can I stop encryption attribute to be copied
together with file?