I am testing an upgrade of a 2016 Server farm to SharePoint Server 2019. I'd originally done a test of one content DB to it's own web app. After ironing out some issues found there, we did a test of all content DBs. Having forgotten about the initial test, of course the copy of that same content DB on a new web app came in with zero sites due to already having those sites existing in the other web app. I detached the original test content DB and deleted the original test web app, but even after detaching/reattaching the content DB on the new web app, it still shows 0 sites.
I have double checked the allwebs table in SQL to confirm that it is the correct database (and not an accidentally created empty DB). I have tried attaching in both the Central Admin site and via Powershell. Tried the RefreshSitesInConfigurationDatabase() command on the new database after removing the old web app. Test-SpContentDatabase does not show any orphan webs.
Anyone have thoughts beyond blowing away the new web app, make a new new web app and reattach all the content DBs (3) to the new new web app? One other note, the other 2 content DBs on that web app are working fine.