I had this happen to me last week. There was an issue where ' nwjs ' just didn't close properly, causing a memory leak. It was using upwards of 12GBs of RAM.
For myself, all I had to do was open task manager and manually close nwjs.
Optionally, restarting your computer will result in the same effect if you're uncomfortable with closing processes in task manager.
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.