I'm facing a really strange behaviour in SharePoint 2019 Standard Server (in all three tiers!) First things first: It's a SharePoint 2019 Standard Server (latest patches already installed) on a Windows Server 2019 Datacenter with SQL Server 2019 Standard in the background.
Generating the three farms (dev/test/prod) was fine and Central Administration is available as it should. Unfortunately every other Web Application that is created afterwards fires a "Service Unavailable - HTTP Error 503", regardless if the Web Application was created with a hostheader or not. I can't find any differences between those Websites/Application Pools in IIS. Besides the physical paths, IDs, etc., everything seems to be similar. As of IIS Manager the websites are online, the application pools are started.
I don't know where to look at now. Maybe some of you might have any idea...
I already checked this page: http://sharepoint-wiese.de/http-error-503-the-service-is-unavailable/ and did all of the three mentioned steps (checking running state of application pools, membership of IIS_IUSRS user group, local security policies). Again: Everything's fine.