where did you store your project?
if the folderpath breaks the networking rules, then all browsers have problems loading files.
can you start the projects index.html directly instead of using the playtest button?
if you can start directly it might point to a problem with the internal chromium-based browser and its settings
if absolutely nothing happens, it might also be that the game is blocked by your antivirus as a false positive of an infected website - a lot of antivirus programs can't see the difference between a remote website trying local access and a local html file trying local access.