Guides / Slack messages not sending or notifications not arriving

Last reviewed 5 Oct 2026

Slack messages not sending or notifications not arriving

Slack messages stuck with a red warning, or notifications not coming through? Connection test, cache, notification settings, and workspace limits.

Two different complaints get filed as "Slack is broken". In one, messages sit with a red warning and never post. In the other, messages arrive but nobody gets notified. They have different causes, so split them first.

Is it Slack?

Open the Slack status page. We read Slack's official status API, which names active incidents and the features affected, such as messaging, notifications or connectivity. If that is clear and colleagues are posting normally, the problem is on your side. If Slack will not load at all, read Slack not loading instead.

Messages not sending: user steps

1. Look for the connection banner. "Trying to connect" or "Connecting" at the top of the window means the app has lost its live connection to Slack. Messages will queue until it returns.
2. Try the browser. Open your workspace at app.slack.com in a private window. If you can post there, the desktop app is the patient.
3. Clear the desktop cache. In the desktop app, open the Help menu → Troubleshooting → Clear Cache and Restart. This does not delete messages.
4. Network path. Slack holds a long-lived secure WebSocket open. Proxies doing SSL inspection, and full-tunnel VPNs, cause messages to hang then send in a burst. Test on a phone hotspot. If that works, the office network is the fault.
5. Channel permissions. Some channels only let certain people post, such as announcement channels. Archived channels accept nothing. Slack usually says so in the message box.
6. File limits. Very large uploads fail on slow connections. Try a link instead.

Notifications not arriving: user steps

• Do Not Disturb and notification schedules. Check whether you have paused notifications or set hours in Slack's preferences.
• Per-channel settings. Channels can be muted or set to mentions only.
• Mobile timing. By default, Slack sends phone notifications only when you are inactive on the desktop. If the laptop is open, the phone stays quiet. Change the mobile timing in preferences.
• Operating system. Windows Focus, macOS Focus, and phone Do Not Disturb all silence Slack. Check that the OS allows Slack notifications at all.
• Test it. Slack's notification preferences include a troubleshooting option that sends a test notification. If the test does not arrive, the block is on the device.

Network and admin checks

• SSL inspection and proxies. Add Slack's domains to your inspection bypass list if websockets keep dropping. One office, one proxy, green status pages — that is the giveaway.
• VPN. Full-tunnel VPNs that route Slack through head office add delay and drop connections. Split tunnelling for collaboration tools is common practice.
• Workspace settings. Admins control who can post in which channels, message retention, and whether external Slack Connect channels are allowed. A retention policy is not a sending failure, but it is often reported as "messages disappeared".
• Free plan history. On Slack's free plan, older message history is hidden after the plan's limit. That looks like "old messages not loading", but nothing is broken.
• Enterprise and SSO. If sign-in to Slack goes through Okta or Entra, an expired session can stop posting until the user signs in again.

When to escalate

Escalate to Slack when the status page shows a messaging or connectivity incident, or when users on different networks and devices all fail at the same time. Slack support will ask for your workspace URL, the time with time zone, and any error text. If it is one office, it is the office network; if it is one person, it is their device or settings.

Related status pages

• Slack
• Amazon Web Services

Related guides

• Slack not loading: is AWS down?
• How to tell if a service is down or it's just you
• VPN connected but no internet or can't reach internal sites

FAQ

Why won't my Slack messages send?

Usually the app has lost its connection to Slack because of the network, a proxy, or a VPN. Check for a 'Trying to connect' banner, try Slack in a private browser window, and clear the desktop app cache.

Why am I not getting Slack notifications on my phone?

By default, Slack only sends mobile notifications when you are inactive on the desktop. Do Not Disturb, notification schedules, muted channels and phone Focus modes also stop them.

Does clearing the Slack cache delete messages?

No. Messages are stored by Slack. Clearing the cache only removes local data, and the app downloads it again.

How do I know if Slack is down?

Check Slack's official status, which we mirror on our Slack page. If there is no active incident and colleagues can post, the problem is local.