Lot's of possible reasons. Bypass the aggravation and do it yourself. Search on Microsoft's Media Creation Tool, download the 64 bit ISO, and do the installation. Have done it on four machines from 3  to 10 years old with minimal problems. My daughter's one year old Inspiron 17 did receive the official download and also installed OK.
Hello everyone! Im using a Dell Inspiron 5447:Intel I7 4510U 2.0GHz, 8.0 GB ram, 1 TB HD, Win 8.1 (64bit), 2GB AMD Radeon R7 M265. I have all the updates available for Win 8.1, Ive done everything it says in the Dell support web page to get Win 10 , Ive checked everything in the (Get Win 10) in Microsoft support web page, and still have nothing. When I open in my laptop the SupportAssit app, and open get support for my Dell Inspiron 5447 and it send me to the webpage, and in the diagnosis site it says: Update to Win 10 is avaliable for your computer, learn more here. I click there and do everything it says, and still nothing. Ive checked if my dell inspiron 5447 does not support win10, but in every web page ive checked it says that my laptop can run win10. What can i do to get Win10 or any other solutions? Thank you very much!
Can´t upgrade to Win 10, why?