I am not sure whats going on but there is a new method this program is trying to use to install and it just doesnt work.
When you first go to the link to click on download cheat engine 6.5.1 it has you go to a present I made a video to show it in action it makes you install a extension and it just doesnt work.
Someone asked darkbyte about this this is what was said
Honestly I will just go to the github version of cheat engine
Latest is 6.5.1