As BBO says, this is a security certificate issue. However, it has nothing to do with out-of-date computers, operating systems or web browsers. It is the BBO security certificate that is out-of-date. My (up-to-date) Kaspersky security software is blocking access to BBO from my up-to-date Edge browser running on up-to-date Windows 10. I haven't found a way of releasing the block and I'm not prepared to disable my anti-virus protection. Fortunately I haven't allowed Kaspersky to install plugins for the Chrome browser, so I can get to BBO using that instead. But BBO needs to sort out its security certificate quickly.