Some time in July Chromium (thus Google Chrome and the Chromium-based Edge browser) introduced a new security control which prevents resources within your local network from being accessed by external websites.
What does this mean? Well, historically it has been possible for a publicly accessible website to make javascript calls to access devices on the local network using their IP address. This is exactly how myplayer.blue works - it is a publicly accessible website that calls APIs which are hosted on BluOS devices on your internal network.
The Chromium update now makes that impossible without explicitly granting myplayer.blue a security exemption in the browser settings to allow it to access what it terms "Insecure content". This is easy to do in both Chrome and Edge, so the bottom line is that myplayer.blue will still work with these browsers, but you'll need to add the exception in those browsers.
Good news is that Firefox has not implemented this, and browsers in Smart TVs such as Sony and LG have also not implemented this, so these still work just fine, no intervention required.