Hi Arbind. I'm Greg, 10 years awarded Windows MVP, specializing in Installation, Performance, Troubleshooting and Activation, here to help you.
Is there some reason you're opening Slack from Edge instead of from Slack Desktop App itself?
Make sure you used this download for Mac and then open it directly to sign in: https://slack.com/downloads/mac
If I'm misunderstanding or there's some other reason you need to open Slack desktop app from Edge, please let me know.
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