Check what changed
Compare a sensible date range against the campaign goal. Look at delivery cost, response and the outcome after the click. Read frequency alongside these measures rather than using a fixed retirement threshold.
Also check the offer, stock, landing page and tracking. A broken form or unavailable product needs a different fix from a tired creative.
Separate the idea from its execution
A concept is the customer problem, objection or use case behind the ad. Its execution is the copy, imagery and format used to express it. A stronger execution may extend a useful concept; a different concept tests a new reason to care.
Keep the next ideas ready
Build a short list of customer questions and untested angles. Identify the assets needed for each one and prioritise ideas that would teach you something different.
Decide what to retain, revise or stop
Review the ad against its purpose. If it attracts relevant attention but weak enquiries, check the promise and destination. If the message is sound but hard to grasp, improve the execution.
Run the next useful test
Choose a clear question, a goal-relevant measure and a budget that gives the test enough activity. Record the result and use it to plan the next creative.
Use the pattern to choose the next check
If delivery cost rises while click response and the post-click outcome stay similar, check auction and audience changes before replacing the message. If clicks hold up but completed enquiries fall, test the offer, form and destination. If response weakens across repeated exposure, compare a fresh execution with a different concept. These are diagnostic starting points; several causes can occur together.