"Your connection is not private" when open website with specific root domain

I have a problem, every time when I open a website with the root domain "io" (example.io), the browser told me that "your connection is not private" (Chrome) or "Did Not Connect: Potential Security Issue" (Firefox). Sometimes I got this note or this and if I keep proceeding to that website, it will appear 404 - Not found.

Actually, I have a workaround with this issue, "using vpn in browser". But, I don't want every time I open .io website I need to activate the vpn. Besides that, if my request is from terminal/cmd it also failed, and I can't use vpn in the terminal/cmd. Can you help me? thank you

PS. Ohh.. and one more, I currently using a mac and not using a proxy. I don't know if this issue happens with other root domain, but I still figured out in .io