FILE PHOTO: The Slack Technologies Inc. logo is seen on a banner outside the New York Stock Exchange (NYSE) during thew company's IPO in New York, U.S. June 20, 2019. REUTERS/Brendan McDermid

SAN FRANCISCO (Reuters) - Shares of Slack Technologies WORK.N were down about 1% in extended trade on Friday after the messaging software company said it was still working to resolve reports of downgraded performance from some users.