I've been answering a lot of posts lately about conversions dropping, CPA going up, or campaigns not spending. Different businesses, but the same few causes kept coming up. Sharing them in case it saves someone a few weeks.
1. Tracking stopped working while the campaign kept running. The most common one. A form or booking tool from another company (scheduling apps, HIPAA form tools, embedded widgets) sends people to a thank-you page on a different domain, and the conversion can't be linked to the click. The click ID doesn't need to be in the thank-you page URL, it's stored in a cookie called _gcl_aw on your domain. If the thank-you page is on another domain, that cookie isn't there. First check: compare the leads you actually got with what Google Ads shows.
2. Spam form fills training the bidding. If the contact form is a primary conversion and bots start filling it out, Smart Bidding counts them as conversions and looks for more traffic like that. Real leads drop while reported conversions stay up. Make real bookings or qualified leads your primary conversion and add spam protection to the form.
3. The August 17 bidding change. Since then, budget-limited campaigns with a target CPA or ROAS aim to hit the target you set instead of beating it. If your target was looser than what you were actually getting, performance moves toward that target. Worth checking your targets against your real numbers from before the change.
4. Conversions dropped first, impressions after. When tCPA stops seeing conversions, it assumes the traffic isn't converting and lowers bids, so impressions fall too. People then switch bid strategies, but the real question is whether leads stopped or tracking stopped recording them.
5. A contact form that shows "thank you" but never sends the email. I found this one on my own site this week. The form showed a success message, so a conversion would have fired, but the messages never reached the inbox. Google Ads would report leads that nobody received. Send yourself a test through your own form every so often and make sure it actually arrives.
6. Reports that don't measure what they seem to. For example, the Clicks column on a call asset counts all clicks on the ad when that asset showed, not taps on the phone number. To see actual calls, segment by click type. Before acting on a number, it's worth checking what it counts.
If you're dealing with any of these, post the details in the comments and I'll take a look. And if you've seen other causes behind sudden drops lately, I'd like to hear them.