Our development team simply does not give us even a vague estimate of one, because of the complex nature of their work.
Oof, that’s rough. I understand not giving a public estimate. I don’t understand throwing the development team under the bus like this. Just say there’s no public estimate and leave it at that. This makes it sound like the development team has no idea what’s going on, which isn’t great to release publicly. Because once a root cause is identified at least a “SWAG” estimate should be possible internally.