Any luck getting it to load? I've had this happen once or twice, but was able to eventually get it to open. Are you using Beta, or Stable release of Construct 3 while working on the project? I can try loading it on my end, of you'd like.
General troubleshooting. I would clear out your entire browser. History, cache, cookies, etc. If you are running from a local copy of Construct 3. Uninstall it, then re-install the version you were using from the Scirra website. Just load that version on Scirra, then install a local version again. Could also test an alternative browser if all that fails.. Chrome, Brave, Firefox, etc.