I've been running Meta for B2B lead gen since 2020, and I see this pattern all the time. A three-day zero-conversion dip is almost never creative fatigue - it's account trust decay or pixel/tracking failure. If your EMQ (Event Match Quality) is below 7, Meta can't reliably match conversions to users, so it's optimising blind. The model degrades fast.
Check your Events Manager:
# Pseudocode for sanity check
if emq < 7:
print("Fix event dedup or CAPI")
elif domain_review_flagged:
print("Account trust dropped")
Event dedup misconfigured or CAPI not sending properly halves your reported conversions - Meta thinks you're getting 50% of actual ROAS. Account trust can tank if your BM has too many old failed campaigns or domain review flagged a claim. Auction prices you as higher risk.
The thing about 10 ads in one adset is real: Meta weights winners internally. But turning off non-winners while the adset is still profitable can collapse everything. The top two ads rely on losers' audience data to improve targeting - kill the noise and you kill the signal.
One caveat: if all competitors in your niche launched at the same time, you're just saturated. Harder to pinpoint without seeing account metrics.
What's your EMQ sitting at? That'll tell you half the story.