Can't see see event notifications for branches in Slack

I’m trying to set up event notifications for Slack, using Gitlab Integrations. I have set up Slack notifications, everything’s set to default settings. I’ve added the webhook for the Slack channel and “Notify only default branch” is unchecked, like so:

When I make changes to the master branch, which is set as default and protected, I get notifications sent to Slack, so that is working. However, the dev branch, that I have set up sends no notifications.

Pressing “Test settings and save changes” also only sends status on Master and not dev branch.

The trigger for Push events has been set and left blank, like so:

Are there any additional settings, that I’m missing somewhere?