Arc Analytics works with public, private, and shared Slack channels.
But, if you change a channel from public to private you could run into a problem where Arc stops sending your messages to your newly private channel.
To keep receiving your Google Analytics reports after you've changed a Slack channel to private:
Log into the Arc Analytics
Select Channels from the top menu on the dashboard
Select + Add to add a new Slack channel and choose your new private Slack channel. This will grant Arc new permissions to send messages
Select Reports from the top menu on the dashboard
Select a report that uses your private channel
Select the Preview in Slack link to ensure messages are sending properl