expert II 24 lx do not see register marks

regards! I am from buenos aires argentina and I buy a gcc expert II lx to make contour cut of adhesive paper that I print on an HP t120. the design I do in illustrator cs6 corell x7 or directly in great cut4. I put out contours and registration marks (try all modalities) and some files cut them perfectly, but most of them are lost by not finding the registration marks on the paper. search, install from scratch, check incompatibilities in windows 7 but nothing my plotter does not cut contours. Now reviewing files, I find that in Great Cut, it shows me the perfect file, but when I preview, the registration marks disappear !!!! if I check with files that were cut well, in the preview I see the registration marks when cutting. in which marks do not appear in the preview the optical reader is lost in the search and gives errror. Question: does anyone have any idea what may be happening to me?

Thank you
from buenos aires using google traslate!