Solution for: Error: Cookies are blocked or not supported by your browser. You must enable cookies to use WordPress

On some clients' website built using WordPress, there was this error:

Cookies are blocked or not supported by your browser. You must enable cookies to use WordPress

If you also have a WordPress website where you are seeing the error "Cookies are blocked or not supported by your browser. You must enable cookies to use WordPress" when attempting to login, please find the solution below.