Check the cover DPI, it should be 300.
If it is 300, try these:
Set scaling to 100%, fit to page off, centering on on both horizontal and vertical.
If the DPI is 96 set scaling to 32%, other settings same.
If the DPI is 72 set scaling to 24%, other settings same.
These assume cover is from main site, covers from the boards are not nessarily measured correctly.