joelc13866394 I did some trouble shooting and was able to confirm that engineering are aware of the CORB issue that is affecting chrome v73 and above. This issue affects both at.js 1.x click-tracking requests, as well as at.js 2.x display and click-tracking notifications.
I am checking with them on the ETA for the fix. Will post the same here once I get an update on the same.
Cross-Origin Read Blocking (CORB) is a web platform security feature that helps mitigate the threat of side-channel attacks (including Spectre). It is designed to prevent the browser from delivering certain cross-origin network responses to a web page, when they might contain sensitive information and are not needed for existing web features. For example, it will block a cross-origin text/html response requested from a <script> or <img> tag, replacing it with an empty response instead. This is an important part of the protections included with Site Isolation.
Chrome's CORB algorithm seems to be fickle. For some reason it doesn't block a JSON response when I use the getOffer method, which is practically the same thing as the JSON response when using the Measure by click element.