Adaptive Card doesn't render TableCell Element containing a RichTextBlock

Dear @AdaptiveCard_Mess,

Thank you for reaching out to Microsoft Q&A forum

I understand that you're experiencing an unexpected issue where an adaptive card containing a TableCell element with a RichTextBlock does not render correctly in Microsoft Teams. Based on my research, since this workflow was working previously and has only started failing recently, it appears there may be a rendering regression in the Microsoft Teams client that is affecting Adaptive Cards. This means that while your JSON payload remains valid, recent updates to the Teams "renderer" have caused issues with displaying RichTextBlock when nested inside a TableCell.

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In Adaptive Cards, RichTextBlock is not rendered in all hosts and has specific limitations that can cause exactly this kind of issue when used inside a TableCell.

Key points from the schema and renderer behavior relevant to this scenario:

1. TableCell.items must contain only supported element types TableCell.items allows these element types:
   • ActionSet, ColumnSet, Container, FactSet, Image, ImageSet, Input.ChoiceSet, Input.Date, Input.Number, Input.Text, Input.Time, Input.Toggle, Media, RichTextBlock, Table, TextBlock. If the payload contains an element type that the host (Teams) does not support, the renderer must ignore that element and continue rendering the rest of the payload. This can make a whole cell appear “empty” even though the JSON is valid.
2. RichTextBlock support is host-dependent While RichTextBlock is part of the schema, not every host or platform version supports it. When a host does not support RichTextBlock, the renderer must ignore that element. If the right column’s TableCell.items contains only a RichTextBlock, the entire cell will appear blank.
3. Markdown vs. RichTextBlock
   • TextBlock supports a subset of Markdown and is the recommended way to format text in most hosts.
   • RichTextBlock does not support Markdown and must be styled via its own properties. If the right column was recently changed from TextBlock (with Markdown) to RichTextBlock, or Teams updated its Adaptive Card host version/behavior, this could explain why it suddenly stopped rendering.
4. Required properties on TableCell TableCell.items is required. If the RichTextBlock is the only item and is ignored by the host, the cell effectively has no renderable items, so the column appears missing.

Practical remediation steps:

1. Replace RichTextBlock with TextBlock in the TableCell that is not rendering, and use Markdown for formatting where needed.
2. Validate the card JSON in the Adaptive Cards Designer / Card Payload Editor to ensure the payload is valid and see how it renders in a generic host.
3. Ensure the card’s declared schema version and the Teams host version align with the features being used (e.g., Table and TableCell require schema 1.5; RichTextBlock support may vary by host implementation).

If, after replacing RichTextBlock with TextBlock, the right column renders again, the issue is due to host support for RichTextBlock inside TableCell in Teams.

References:

• Adaptive Card Renderer Specification
• TableCell Element
• AdaptiveCard Element
• Known issues for Adaptive Cards in Viva Connections Mobile
• Create your first adaptive card