I cant find my 2015 tax return. I used CDROM to file 2015, but I cant find the PDF of the 1040, so I downloaded it from my online account, but it just comes out blank.

Sorry, but if you used the downloaded version then the return is only on the computer you used to complete the return ... it will not be in the ONLINE account.   Using the 2015 program open the return and save it as a PDF.