What did this app do exactly? It was just a reporting app, I'm assuming that the source data collected, albeit perhaps in different formats, lived somewhere else and that there wasn't a lot of data or a lot of variations. From my understanding it seems there was an Auth0 redirect issue, but why wasn't this just a night of taking the source data and doing scripting then shipping out the reports via a secure DropBox type service? We've all be there where an ETL job fails, since it isn't critical (e.g., financial transaction), it wasn't tested every which way and we just had to some scripting.
Even if it is, say, 500TB of data, in 300 different formats usually those formats aren't drastically "different." Maybe I'm not understanding what the application was supposed to do to not understand why this wasn't solved every quickly. Or maybe given the timeline it was solved quickly once the right people got involved and figured out what needed to be done.