FearLess Cheat Engine

What happens is that whenever I try to activate (either using F1 or clicking on Activate), it takes a few seconds, freezes, then close down. I've tested with two games, Minecraft Dungeons and Final Fantasy I Pixel Remaster. What can I do to fix it?

CE doesn't have an "activate" button with an F1 hotkey, this sounds more like a trainer/table. Likely it's out of date and needs to be updated. You'll need to ask the creator where you downloaded the trainer/table from.