Hi,
If your power button is physically damaged or worn out then you will need to replace it.
Here’s a link to YouTube video showing how to do this:
https://duckduckgo.com/?q=honor+8+power+button+not+working&t=braveed&iar=videos&iax=videos&ia=videos&iai=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DEa_hhtT5rNU
If you don’t feel confident enough then you can get a repair shop to give you a quote on how much it will cost.
Hope this explains what is required in replacing the power button.