Copilot Studio (Agent → Add knowledge): .docx upload hangs or shows “File type not supported”

Question

We’re adding files to an agent via Copilot Studio → Agent → Knowledge → Add. Multiple customers report that .docx uploads either spin indefinitely or return “file type not supported”, while PDF/XLSX/PPTX upload and index normally.

Environment & Symptoms

Channel: Copilot Desktop app (WebView2) and browser (Edge/Chrome) both observed.

Action: Local file upload / drag‑and‑drop of .docx → “file type not supported.”

Control tests: PDF/XLSX/PPTX succeed; SharePoint/OneDrive‑stored file selection sometimes works; desktop app shows more frequent spins.

What we already ruled out (file side)

Re‑saved in Microsoft Word as Word Document (*.docx) (not docm), no password, no macros, no digital signature.

No IRM/sensitivity labels; small file (not 0 bytes, far below size limits).

Simplified path/name (e.g., C:\Temp\test.docx) and retried.

What we already tried (client/app side)

Desktop app sign out → quit → relaunch → sign in, and App Repair/Reset in Windows settings.

Edge/Chrome fresh session and in‑private; third‑party cookies ON; cache cleared.

OneDrive/SharePoint upload → select from library as knowledge source (mixed results).

We need a repeatable diagnosis path and authoritative guidance to explain why only .docx fails in Add‑knowledge for this tenant, and how to remediate. If there is an existing bug report related to this issue, please share the details or reference link.

Answer 1

Hello Jin Hyun Park,

The current .docx upload failures in Copilot Studio are caused by a mix of environment settings, service bugs, and file-level issues. The problem appears across both browsers and the desktop app, with other file types uploading normally. In many tenants the issue is triggered when Dataverse Search is disabled or when file-upload policies restrict Copilot Studio’s ability to index knowledge sources.
Microsoft has also acknowledged an intermittent backend bug that affects .docx processing, especially following recent updates.
Uploads can fail if the file contains corrupted metadata or if a previous failed attempt left a stale record under the same name. Supported file requirements remain unchanged: .docx files must be unprotected, under 512 MB, and saved in a standard Word format. Effective troubleshooting involves confirming environment settings, validating the file, testing upload via SharePoint or OneDrive, and checking Microsoft service health. Temporary workarounds include renaming the file, switching browsers, or using SharePoint/OneDrive as the upload source.

Reference Document-https://learn.microsoft.com/en-us/microsoft-copilot-studio/knowledge-add-file-upload