Google added a Channel Diagnostics section to Performance Max in the first week of July, and it answers the question channel-level reporting raised in the spring: why a given channel is underdelivering. The report shows, per channel, which missing or disapproved assets are limiting delivery, down to the specific asset type 1. It is the second read-only window Google has opened into pMax this year, and the more useful one, because it converts channel underdelivery into a concrete creative to-do list. Treat it as a monthly 15-minute check, not a dashboard to stare at.
What the report shows, and where to find it
Channel Diagnostics lives under Insights & Reports, inside the Channel Performance view, and it reports asset gaps for each of the six surfaces Performance Max serves: Search, Display, YouTube, Discover, Gmail, and Maps 1. For each channel it flags the missing or disapproved assets limiting delivery, down to asset type: headlines, descriptions, images 1. The feature was spotted in the wild on July 1, 2026, with no formal announcement from Google 1.
The specificity is the point. A generic “limited by ad strength” nudge invites guesswork. A flag that says Display delivery is limited because the asset group has no images is not analysis; it is a work order. The pMax Channel Diagnostics report ties missing assets to the channel they are starving, which is the first time Google has drawn that line for you inside the product.
Disapprovals get the same treatment, and they deserve separate attention. A missing asset is a production gap you brief to a designer. A disapproved asset is a policy problem that quietly caps delivery until someone appeals or replaces it, and it tends to sit unnoticed because nothing in the campaign looks broken.
One caveat before you go looking. Unannounced features tend to roll out unevenly, and this one surfaced without a blog post or a help-center entry. If the section is not in your account yet, that is a rollout question, not a you question. Check back on the next monthly pass rather than assuming the account is excluded.
The second window this year, and the sharper one
Channel-level visibility into Performance Max arrived in stages, and each stage changed what an operator could do. In April we wrote about the channel performance timeline, the report that finally showed where the money goes across channels. That window shows outcomes: this much spend went to YouTube, this much to Search. Diagnostics shows causes: YouTube is underdelivering because these assets are missing or disapproved. One tells you what happened. The other hands you the fix.
The stakes are not niche. Performance Max accounted for 67% of Google Shopping spend and 68% of Shopping sales in Q1 2026, per Tinuiti’s benchmark report 2. A report that explains underdelivery inside pMax is a report about the majority of most retailers’ Google budget. When two-thirds of Shopping spend runs through one campaign type, a window into why that campaign type withholds delivery is worth 15 minutes of anyone’s month.
How to run the monthly check
The check runs in four moves and should not take longer than a coffee. Open Channel Performance and find the Diagnostics section. Note which channels flag limited delivery. Write down the missing or disapproved asset types per channel. Brief the gaps into the next creative sprint, then recheck on the next monthly pass to confirm the flags cleared.
The briefing step is where the value either materializes or leaks. A flag is not a ticket until someone translates it. Missing headlines and descriptions are copy hours, usually a small batch an experienced writer clears in an afternoon. Missing images are design work, sized and cropped to the asset group’s requirements rather than pulled from whatever the brand folder had lying around. Disapproved assets are a different lane entirely: someone has to read the policy reason, decide whether to appeal or replace, and own the follow-up, because an unresolved disapproval caps delivery just as effectively as an empty slot.
There is also a quiet measurement benefit in the recheck. When you clear a flagged gap and then watch whether that channel’s delivery moves on next month’s pass, you are running the closest thing to a controlled input test pMax allows. Asset in, delivery response observed, one variable at a time. Few accounts bother, which is exactly why the ones that do learn faster than their category.
Resist the urge to check it weekly. The report is read-only; there is no lever inside it, and asset production cycles do not turn fast enough to make a weekly look worth anything. The same discipline applies here that we recommended for reading pMax search terms: schedule the look, extract the action, close the tab.
The one trap worth naming is treating every flag as an obligation. Google flagging that Gmail delivery is limited does not mean Gmail delivery deserves rescue. If a channel has never produced converting traffic for the account, a missing-asset flag on that channel is information, not instruction. Fill the gaps on the channels that carry revenue first, and let the marginal surfaces wait.
Every window points at the same inputs
Performance Max is still a black box, and Google shows no sign of opening the bidding logic or the channel allocation to advertiser control. What Google keeps adding is windows: search terms visibility, channel-level performance in the spring, asset-level diagnostics in July. Three windows, one conclusion. Every one of them terminates at the inputs the advertiser controls, which are creative assets and the feed.
That is why the fix for a Diagnostics flag routes through creative production, not campaign settings. There is no setting to change. There is a missing headline, an absent image ratio, a disapproved description, and the hours go to producing and replacing those. On the accounts we manage, Diagnostics findings feed the creative queue directly, because that queue is where pMax performance gets made.
Assets are also only half the input surface. The feed is the other half, and Diagnostics says nothing about it, so do not mistake a clean Diagnostics report for a healthy campaign. Titles, product types, availability, and price accuracy shape what pMax can do with the assets you supply. The report tells you when the creative cupboard is bare; the feed audit tells you whether the product data underneath deserves the creative at all. Run both, on the same monthly rhythm.
Operators keep asking Google for bidding controls, and Google keeps answering with reports about assets. At some point the pattern is the message. The platform has told you, three windows in a row, where the leverage sits.