Troubleshoot MM Blocks

Available on Entry, Professional, Enterprise, and Enterprise Advanced plans

Integration posts that use MM Blocks show structured content—including text, images, buttons, and menus—directly in a channel. This page covers common issues when MM Blocks do not render or respond as expected, with emphasis on mobile clients.

MM Blocks content does not appear

Symptoms: A post shows only plain text (or no content) and the expected buttons, images, or content blocks are missing.

Try the following:

1. Update your client. MM Blocks require a current Mattermost web, desktop, or mobile app. See client availability for platform support.

2. Confirm the integration payload. The post must include a non-empty props.mm_blocks array (or a legacy format such as message attachments that the client translates). Ask your integration owner or system admin to verify the webhook or bot payload.

3. Check the feature flag (system admins). Self-hosted deployments can disable MM Blocks by setting MM_FEATUREFLAGS_MMBLOCKSENABLED=false. When disabled, native MM Blocks payloads are not rendered and their actions are rejected.

4. Reload the channel. Pull to refresh on mobile, or switch channels and return, to fetch the latest post data.

Buttons or menus do not respond

Symptoms: Buttons appear disabled, or tapping a button or menu option has no effect.

Try the following:

1. Wait for the action to finish. Some integrations show a loading state while Mattermost calls an external service. Slow integrations may time out based on your server’s integration request timeout setting.

2. Check whether the control is disabled. Integrations can send buttons and menus in a disabled state. Disabled controls cannot be activated.

3. Verify outbound server connectivity. External actions require Mattermost server nodes (not end-user devices) to make outbound requests to each integration action endpoint URL configured in the post. These endpoints typically use HTTPS on TCP port 443; if a URL uses another scheme or port, that destination must be reachable outbound from the server. Allow only the specific integration endpoints your organization uses—this is not an inbound connection requirement.

4. Look for follow-up messages. Successful actions may update the original post or return an ephemeral reply visible only to you. Check the thread panel if the post is part of a thread.

Scrollable content issues on mobile

Symptoms: Clipped integration content cannot be expanded, or the Scrollable content screen is empty.

Some integration posts limit the height of a content region. When content overflows, Mattermost mobile shows a clipped preview with an expand control in the corner of the region.

To view the full content on mobile:

1. Locate the clipped region in the post (a fade at the bottom indicates more content below).

2. Select the expand control in the bottom-right corner of the clipped area.

3. Mattermost opens a full-screen Scrollable content view where you can scroll through the complete block content.

4. Use the back gesture or navigation control to return to the channel.

If the Scrollable content screen shows “Cannot display content”:

• Return to the channel and open the expand control again. This screen appears when the expanded payload is no longer available (for example, after navigating away before the view loaded).

• Update to the latest mobile app build if the issue persists across multiple posts.

On web and desktop, the same clipped regions scroll inside the post; a separate full-screen view is not used.

Collapsible sections or images look wrong

Symptoms: A section will not expand, an image fails to load, or part of the layout is missing.

Try the following:

1. Collapsible sections: Select the section header to toggle between expanded and collapsed states. If the header is missing or empty, the integration payload may be incomplete.

2. Images: External images require a valid URL and may be blocked by your server’s image proxy or SVG settings. Contact your system admin if images from other integrations load but MM Blocks images do not.

3. Partial content: Clients skip individual malformed blocks and still render valid ones in the same post. If only some elements are missing, the integration payload likely contains invalid block entries.

Not all blocks appear or text is cut off

Symptoms: Only part of an integration post renders, blocks at the end of the post are missing, or text in a block or on a button label ends abruptly.

Mattermost enforces size limits on MM Blocks payloads. Content that exceeds a limit is truncated when the post is rendered.

Try the following:

1. Review payload limits (integration owners). A single post is limited to:

   • 100 blocks in the props.mm_blocks array

   • 32 levels of nesting depth across nested block structures

   • 16,000 characters total across all text in the payload, including text blocks and button labels

2. Reduce payload size. Split long content across multiple posts, shorten labels, flatten deeply nested structures, or remove optional blocks.

3. Validate after content changes. If truncation appears only for certain posts or started after an integration update, compare the payload against these limits.

Legacy message attachments

Older integrations that use message attachments are translated into the MM Blocks UI at render time. Button and menu behavior should match native MM Blocks posts. If an attachment-based post behaves differently from a native MM Blocks post, report the payload to your integration owner.

Get more help

• End users: See Extend Mattermost with integrations for how to use buttons, menus, and expandable content in channels.

• Developers: See the MM Blocks reference for payload format, action APIs, and migration guidance.

• Mobile deployment issues: See Mobile deployment troubleshooting for connectivity, push notification, and app install problems unrelated to MM Blocks content.

If you continue to experience issues, visit the Mattermost Troubleshooting forum or contact your system administrator.