Hi @cbsimp - This needs to be debug and might be couple of things to check
here are some pointers for you.
1) Check your activity qualification - audience criteria, priority in the case of multiple activities on same location.
2) A4T integration - check the activity linked to correct report suite, post_tnt configured.
3) how your target implementation has been setup, are you using at.js / websdk?
if websdk - check alloy.js passing the activity data correctly
if at.js - check basic configuration or debug call through mBoxTrace.
see if you're able to get the activity name in post_tnt_action
https://experienceleague.adobe.com/en/docs/target/using/integrate/a4t/a4t-faq/a4t-faq-classifications
This guide help you to understand - https://www.softcrylic.com/blogs/adobe-analytics-for-target-a4t-a-look-under-the-hood/
Try the steps and let us know.