Slack Integration - Deployments

I want to be notified in this one Slack channel of all my Gitlab deployments, successes and failures. I got the Integration (webhook) from Slack. After that, I went to Settings - Integrations -> Slack notifications in 9 of my Gitlab projects, ensured the Active and Deployment checkboxes were checked, added the Slack channel, and set to be notified for All branches.

Now, only one of my projects is notifying me of deployments. When I push the Test Settings button for each project, the latest commit shows up in the channel. Also, if I check the Pipeline checkbox, the channel is notified once the pipeline finishes. However, I simply want Deployments.

Am I missing something?

Thanks all!