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.
When you're in Slack, click Add apps, search tettra, and then click Add on the Tettra Wiki option.
On the next screen, submit a Request to install.
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.
