Slack connectivity and sync issues typically stem from network instability, software conflicts, or misconfigured settings. The most effective troubleshooting begins with verifying your internet connection and Slack’s service status, followed by systematic checks of app updates, firewall/antivirus interference, and network configurations. For persistent problems, Slack’s built-in diagnostic tools—like the connection test and huddles troubleshooting panel—can pinpoint WebSocket disruptions or bandwidth limitations. Sync issues, particularly with calendars like Outlook, often resolve by re-enabling the integration or checking permission settings.

• Primary causes: Unstable internet, outdated apps, firewall/antivirus blocks, or Slack server outages ^[1][4][6]
• First steps: Run Slack’s connection test (Help > Troubleshooting > Run Connection Test) and check Slack’s status page for outages ^[2][4]
• Advanced fixes: Temporarily disable antivirus/firewalls, allowlist Slack’s URLs/ports (WebSockets over port 443), or use tools like PingPlotter to trace server connectivity ^[1][2]
• Sync-specific: For Outlook calendar sync, ensure the integration is enabled via Slack’s settings and permissions are granted ^[10]

Troubleshooting Slack Connectivity and Sync Issues

Network and App-Level Fixes

Network instability and app misconfigurations account for most Slack connectivity problems. Start by isolating whether the issue originates from your local network, Slack’s servers, or the application itself. Slack relies on persistent WebSocket connections over port 443, which can be disrupted by proxies, firewalls, or ISP throttling.

For immediate diagnostics, use Slack’s built-in connection test tool (accessible via Help > Troubleshooting > Run Connection Test). This test evaluates:

• WebSocket connectivity: Confirms if your network allows persistent connections to Slack’s servers ^[1].
• Browser/desktop app performance: Identifies if issues are isolated to a specific platform (e.g., Chrome vs. Slack desktop app) ^[2].
• Latency and packet loss: High latency (>300ms) or packet loss (>1%) often indicates ISP or local network problems ^[2].

If the test reveals WebSocket failures:

• Temporarily disable antivirus, ad-blockers, or VPNs, as these frequently block Slack’s connections. Norton, McAfee, and Windows Defender are common culprits ^[1][4].
• Allowlist Slack’s domains and IPs in your firewall/proxy. Critical URLs include:
• *.slack.com
• *.slack-core.com
• *.slack-edge.com
• *.slack-files.com ^[1]
• For corporate networks, ensure proxies are configured to support WebSockets and not inspecting HTTPS traffic to Slack’s endpoints.

Bandwidth saturation can also degrade performance, particularly during huddles or file transfers. Slack recommends:

• Minimum speeds: 1 Mbps download/512 Kbps upload for voice calls; 3 Mbps download/1 Mbps upload for video ^[3].
• Tools to diagnose: Use PingPlotter to trace routes to Slack’s servers (e.g., slack.com) and collect 10+ minutes of data to identify consistent packet loss or latency spikes ^[2].

Sync and Integration Issues

Sync problems—such as Outlook calendar mismatches or delayed message updates—often stem from permission errors, outdated integrations, or API limitations. For Outlook calendar sync, the most common fixes include:

• Re-enabling the integration: Navigate to Settings > Apps > Outlook Calendar, click “Disconnect,” then relink your account. Ensure you click “Turn On” after linking to activate sync ^[10].
• Permission checks: Verify Slack has calendar read/write access in your Microsoft 365 admin center (for enterprise users) or Outlook settings.
• Time zone alignment: Mismatched time zones between Slack and Outlook can cause sync delays. Set both to the same time zone in their respective settings.

For general message or file sync issues:

• Clear Slack’s cache: On desktop, go to Help > Troubleshooting > Clear Cache and Restart. Mobile users should uninstall/reinstall the app ^[8].
• Check for throttling: Free Slack plans limit message history and searchability. Upgrading to a paid tier may resolve missing messages ^[4].
• Device-specific fixes:
• Windows/macOS: Reset network settings (e.g., flush DNS with ipconfig /flushdns on Windows) or switch from Wi-Fi to a wired connection ^[6].
• Mobile: Enable “Background App Refresh” (iOS) or disable battery optimization for Slack (Android) to prevent sync pauses ^[7].

If issues persist after these steps:

• Collect logs: Generate a Net Log (via Slack’s troubleshooting menu) and share it with Slack support for deeper analysis ^[1].
• Test alternative networks: Use a mobile hotspot or different ISP to rule out local network restrictions ^[6].