Meta assigns every WhatsApp Business API number a quality rating based on how recipients respond. Enough blocks and reports and your rating drops, your messaging limit falls with it, and the channel stops working. Here is what actually causes it.
Five causes, roughly in order
Frequency comes first. Most degradation traces to sending too often rather than sending badly. WhatsApp sits alongside messages from family. Weekly promotional broadcasts read as intrusive in a way weekly email does not.
Weak consent is second. Numbers collected through bundled checkboxes or repurposed from delivery data belong to people who do not remember agreeing. They block, because from their side an unknown business is messaging them.
Irrelevance is third. Broadcasting the same offer to your whole list means most recipients get something with no bearing on them. Basic segmentation by purchase history usually cuts block rates noticeably.
No easy exit is fourth. If opting out requires replying with an exact keyword nobody told them about, blocking is simply easier. Put the opt-out instruction in the message.
Template and reality mismatch is fifth. A template approved as utility that reads as promotional gets reported, and it also risks recategorisation.
Recovering a damaged number
Stop marketing sends entirely. Not reduce, stop. Keep only utility and service messages running for two to three weeks while the rating recovers.
Then re-permission before resuming. Message the list once, explain what you send and how often, and ask people to confirm they want it. Continue only to those who confirm.
Resume at half your previous frequency and watch block rate per send. If it climbs again, the problem is your list rather than your cadence, and the answer is rebuilding consent properly rather than tuning creative.
The preventive habit
Review block rate after every send, and treat any campaign that produces an unusual spike as a signal to change the next one. Teams that only look at revenue find out about a quality problem when their sending limit drops, which is several weeks too late.