Hi @Yavuz Diler ,
If you want to use Windows, you can use add
WEBSITE_NODE_DEFAULT_VERSION application setting and set it to 10.14, see https://learn.microsoft.com/en-us/azure/app-service/configure-language-nodejs?pivots=platform-windows#set-nodejs-version for more details. I would, however, recommend you use either ~10, ~12, or ~14 (which is the latest) just in case a minor version is removed or replaced for any reason.
@Yavuz Diler , in the address bar I see your trying to access
/authroute. Can you hit the site root? If not, is there anything in the logs that you can see with your site failing start up?
@Ryan Hill I have the same case for site root, basically i am trying to run two apps on the same App Service (Windows). I have checked the application logs could not find any anomaly. Also i had the exact same error with a linux app service. But i was able to fix the problem by configuring stack option to Node 10.14.