Open the affected workspace in the Slack desktop app. From your profile picture, go to Preferences → Notifications and make sure Desktop notifications is checked. Resume paused notifications and check the schedule. Ask for a new direct message while another app is in front, then see whether the banner appears.
01Check which messages Slack should notify you about
Section linkIn Slack’s notification preferences, Mentions and direct messages can leave ordinary channel posts without a banner. If a new direct message shows a banner but posts from one channel do not, check the settings for that channel before changing notifications for the whole workspace.
02Check for a pause or schedule
Section linkLook for a snooze icon next to your name. Use the Notifications menu under your profile picture to resume if Slack is paused. Also check the allowed hours: a schedule can silence notifications even when the desktop checkbox is on. Try the same direct-message test during an allowed period.
03Check whether your system is hiding banners
Section linkIf the message arrives in Slack but no banner appears, open the computer’s notification settings and allow notifications for Slack. On Mac, check the alert style for Slack. On Windows, check whether banners are enabled for the app. Check whether a focus or Do Not Disturb mode is suppressing banners, and retest with the same workspace.