I was working a late night rush project. When I came to the point of placing pdf files in my indesign CC document nothing worked. The first files showed up missing their header. They next file simply did not appear on the page. They previewed ok. The eventual work around was to place them in Indesign 5.5, an older program. Then they came in fine. I need to have an answer to why this happened. I was not placing the files from the cloud on somewhere on the internet but from my hard drive. I am getting very frustrated with this new CC application.
Try showing the import options and make sure the crop option you want to use is one that is not grayed out.