Sorry for the delay, I went afk for the holidays. I am still able to replicate this. When I get a chance I will make a quick video in the hopes someone spots a mistake.
Basically nothing is being triggered after approving topic. I am seeing no errors in the events list for the webhook either.
As you can see below I have pretty much set it to send me everything though I have tried limiting to just topic and post actions as well.
When I checked today the last webhook event that executed since 12/22 was for a ping that I sent using the ping button. Though the site has been pretty active since then.
When I can I will create a video of this in action. In the hopes someone has an idea why they are missing.