Hi @CrisciSteve-8248
The PartUnlimited example application is several years old, and it seems like the deployed web app at that URL is no longer available or at least isn't deployed at the moment.
However, all the code is open source and available in this GitHub repo.
https://github.com/Microsoft/PartsUnlimited
And the lab at https://microsoft.github.io/PartsUnlimited/pandp/200.1x-PandP-ManualdeploywithVS2017toAzure.html walks through deploying the web app to your own Azure App Service, so you could walk through those steps and then continue with the testing labs.