Thanks Red90, i did it of course, i tried every ways possible. I loaded, nothing, i deleted, emptied the trash, i turned it on, (even waited for a fix), turned it off, put the gpx file back in, turned it on, nothing.
I tried several times.
Then i loaded a smaller gpx file (around 50 caches), there all are visible.
I thought i got a lucky file that would make every other file as it "unblocked" the device, no, nothing of the second gpx showed.
Then Gushoneybun replied to the topic, i tried to make smaller gpx files (which individually added make the "big" one that doesn't work, around 700 caches), 3 gpx files of around 200 caches each, and every caches are shown.
The solution, that i'm afraid is "rickety", is to load gpx file of arund 200 caches.
( i don't want to try more caches in a file as i don't want to break the luck )