Ad Serving are being limited on some websites because Google works hard to maintain an ads ecosystem that protects advertisers, publishers and users from fraud and bad ad experiences.
As a result, Google may sometimes place a limit on the number of ads your AdSense account can show. This might be a temporary ad serving limit while we get to know you and evaluate your traffic quality, or it might be because we've identified invalid traffic concerns in your AdSense account.
Here's a video how to fix ad limit if any kind!