Hello! I’m facing this issue as well.
- Clearing DNS isn’t possible(?) because I use Arcware to rent VM’s for Pixel Streaming.
- I’ve deleted cesium-request-cache.sqlite, reuploaded the package, and tiles still don’t stream.
- Restarting the machine shouldn’t(?) matter, as the VM’s startup on request.
I’m not sure how installing the Starfield Services Root Certificate Authority from AWS will work, since I rent out VM’s from Arcware, as recommended HERE
My project is packaged to Windows. This issue arrived within the last month. All of my previously uploaded and working projects are broken, failing to load your gorgeous tile sets 
I can provide a link to the Arcware stream and/or .zip package directly to a Cesium Team member, if requested.
Hope to get this fixed soon… Thank you!