User identification is blocked by Adblock Plus
If a visitor is using an Adblock Plus extension, calls to drift.identify() fail because they are blocked by the extension.
As a consequence the visitor doesn't get identified, playbook behaviour based on identification is flawed, and answering to that visitor's requests is made difficult because we don't know who they are.
The fix is probably fairly easy. You need to check, but probably Adblock is only blocking the request based on the URL. If you changed the API URL to something else than "/identify", it would probably go through. You can do that without breaking previous implementation, by keeping the "/identify" URL working, but adding a second equivalent URL, for example "/user-details" or something.
We reproduced this on Chrome 99.0.4844.83 with Adblock plus version 3.12 on Mac OS X 10.11.6, but it is most probably specific to Adblock Plus, so it should be the same on any browser and any operating system.