I bought an hp laptop(hp ts 15-r134cl) about a month ago and I did the recovery media which was in it to my pen drive but unfortunately I have lost my pen drive .Some weeks ago it was infected with virus so I wanted to reset it to it's factory default but I was unable to do that. It was running Windows 8.1 pro so I downloaded windows 8.1 pro iso from the internet and installed it but it didn't requested for any product key and I was able to activate it, so I want to know why it didn't ask for product key. And I have all the windows 8.1updates but the get Windows 10 app is not showing on the taskbar but app is in the system folder (c:windows /system 32/GWX) I have tried it but its not showing on the taskbar. Please I want to know its not appearing because I installed the same version of the windows or my laptop is not supported by windows 10 (hp ts 15-r134cl 4th generation windows 8.1 oem machine) please I really want to know the problem.
The product key is stored on the bios chip and will automatically be injected during installation if the notebook originally shipped with 8.1 pro - just check ( windows Control Panel, System ) that Windows is shown as activated.
Regarding the Windows 10 upgrade app, there's a comprehensive trouble-shooting guide on the following link - see the answer by Yaqub K.