When attempting to dial out from Outreach Voice, the error "Call in progress: There is an existing call in progress, please complete the call before starting a new one." pops up.
To resolve this issue, first try opening Outreach in an incognito window and placing a call there. If this resolves the issue, go through clearing the cache and cookies and making sure Chrome is up to date. If that doesn't resolve the issue, try resetting Chrome.
This is usually caused by a caching issue, so even though the previous call ended, it maintains the state of being connected.