We have something similar at my big corp company. I think the issue is you went from Green to Red in a flip of a switch. A more normal project goes Green...raise a red flags...if red flags aren't resolved in the next week or two, go to yellow...In these meetings everyone collaborates ways to keep your green or get you back to green if you went yellow.

In essence - what you were saying is your boss lied the whole time, because how does one go from a presumed positive velocity to negative velocity in a week?

Additionally assuming you're a dev lead, it's a little surprising that this is your first meeting of this sorts. As dev lead, I didn't always attend them but my input is always sought on the status.

Sounds like you had a bad manager, and Amazon is filled with them.