Pre-mortem your launch

I'm about to launch the thing below. Imagine it's 90 days post-launch and it has clearly failed.

In this scenario:
1. List the five most likely reasons it failed, ranked by probability (not just impact).
2. For each: what would've been the earliest signal we could've caught it? What would we have done differently in week 1?
3. Identify the single highest-risk assumption that, if wrong, sinks the whole launch.
4. Suggest a 48-hour test to de-risk that assumption before we ship.

Be specific. "Marketing didn't work" is not a reason — "we assumed the persona would convert at 3% but the actual cohort runs more like 0.5%" is.

Here's the launch:
[YOUR LAUNCH DESCRIPTION]