I see "You are not authorized to install DX" when I try to Slack OAuth

This article describes what to do if you encounter the following error when trying to Slack OAuth:

You are not authorized to install DX on [workspace]
DX is restricted for this workspace. Please reach out to one of your app managers if you would like additional information or to ask them to install this app.

This error is caused when a Slack Workspace Owner “restricts” the DX Slack App. This Slack help article, under Pre-approve or restrict apps > Restrict apps, describes how a Slack Workspace Owners can restrict apps that have already been installed.

To unrestrict the DX Slack App, a Workspace Owner needs to “Pre-approve” the DX app by following the instructions in the Slack help article. Alternatively, it may be easier to have the Workspace Owner reinstall the DX Slack App by visiting https://app.getdx.com/slack/install. Once this is completed, users should be able to proceed with individual OAuth flows without hitting the “You are not authorized” error page.