The Plugin Portal previously returned a 404 when accessing the root directory. The blank page root page was added a few months ago to make the Nexus and Artifactory behave better when proxying it. It is always blank as the Plugin Portal is not browsable and the main intention was for the root to return a 200 instead of a 404.
As of now, 58 minutes after your original post, I’m not seeing any issues with the Plugin Portal or resolving the plugin using your script. This is just another point of data though. There could be / have been an issue.