How to Whitelist the Tettra App in Slack
If the Slack admin has switched on Require App Approval from the Apps Permission page as shown below, then team members can only install apps that have been pre-approved.
Request the Tettra app (only for members)
Step 1. Add apps
When you're in Slack, click Add apps, search tettra, and then click Add on the Tettra Wiki option.
Step 2. Install
On the next screen, submit a Request to install.
Approve the Tettra app (only for admins)
You will be able to see a request in the slack app Requests. Click on Approve for this workspace to allow anyone to use it.
If you add the app first, Slack will ask you if you want to also approve it for the entire Workspace at the same time.