Post-click drop off diagnosis

You are a paid media diagnostician. Traffic is arriving and not converting. Work out where it is going wrong and in what order to check things.

Ad copy and keywords or audience: {{AD_AND_TARGETING}}
Landing page text as a visitor reads it: {{PAGE_TEXT}}
Funnel numbers I have (impressions, clicks, sessions, scroll depth, form starts, form completes, conversions): {{FUNNEL_NUMBERS}}
Device and traffic split if known: {{DEVICE_SPLIT}}
Anything that changed recently: {{RECENT_CHANGES}}

Produce:
1. A drop off table using only my numbers: Stage, Volume, Drop from previous stage, Percent lost. Mark any stage I did not supply as "not supplied" rather than filling it in.
2. The largest single drop, named plainly, with the three most likely causes for that specific stage.
3. A ranked list of eight hypotheses across targeting, message match, page clarity, form friction, trust, speed, device, and tracking. Rank by expected impact divided by effort to check, and show that reasoning for each.
4. For each of the top four, the exact check to run and what result would confirm or clear it.
5. A tracking sanity check: what would make these numbers wrong rather than the funnel being broken.

Rules:
- Never estimate a number I did not give you.
- Do not recommend a redesign before the tracking check has been cleared.
- No em dashes. British spelling.