Copilot Not Working in Excel? Connection Errors Fixed

When Copilot is visible in Excel but throws errors every time you try to use it, the cause is almost always one of three things: a service outage on Microsoft's side, a Mac-specific desktop app issue, or a rate limit hit from overusing the =COPILOT() function. Here's how to tell which one you're dealing with and what to do about each.

Step 1: Check Microsoft's service status first

Before troubleshooting your own setup, check whether the problem is on Microsoft's end. Copilot in Excel has experienced documented service degradations — including a widespread outage in early June 2026 that affected Copilot across multiple Microsoft 365 apps. Go to status.microsoft365.com or, for business accounts, check Microsoft 365 Admin Center > Service Health. If there's an active incident or degradation listed for Copilot or Excel, the fix is simply to wait — no amount of troubleshooting on your end will resolve a backend Microsoft outage.

Error: "Copilot can't read or write" / "Script execution failed"

This error — especially common on Mac — means Copilot can see your workbook but can't modify it. The most common causes and fixes:

• File not saved to OneDrive with AutoSave on: Copilot in Excel requires the file to be saved to OneDrive (not just locally) with AutoSave enabled. Check the top of your Excel window — AutoSave should show as On. If the file is saved locally, move it to OneDrive first.
• Mac-specific workaround: on Excel for Mac, toggling AutoSave off before entering your prompt and back on afterward can unblock this error for that session — it's a workaround, not a fix, but it works while the underlying issue persists in the current build.
• File format issue: make sure the file is saved as .xlsx, not .xls or another older format. Copilot doesn't work reliably on legacy file formats.
• Excel desktop app version conflict (Mac): this error has been tied to specific Excel for Mac builds — version 16.109.x particularly. Try opening the same file in Excel Online to confirm Copilot works there. If it does, the issue is the desktop app version. Microsoft support has recommended reverting to the previous version while a patch is released, though for most users the simplest workaround is to use Excel Online until the desktop app is updated.

Error: "Excel API is not responding" / "Persistent internal errors"

This error means Copilot has completely lost its connection to your workbook. Work through these in order:

1. Sign out and back in: go to File > Account > Sign out, restart Excel, sign back in. This refreshes your login token, which can expire and cause this exact error.
2. Try a different workbook: open a brand new blank workbook and test Copilot there. If it works in a new file but not your original one, the issue is specific to that file rather than your account or app.
3. Update Office: go to File > Account > Update Options > Update Now. Some builds have known Copilot connectivity bugs fixed in newer versions.
4. Test in Excel Online: open the same file at office.com. If Copilot works there but not in the desktop app, the problem is local — run an Online Repair (Settings > Apps > Microsoft Office > Modify > Online Repair).

Error: #CONNECT! "Too many requests"

This error is specific to the =COPILOT() function and means you've hit Microsoft's rate limit. The =COPILOT() function is limited to 100 calls per 10 minutes and 300 per hour — limits that are easy to hit accidentally when you copy a formula down a long column, since each cell counts as a separate call.

Fixes:

• Wait 15–30 minutes — the rate limit is temporary and resets automatically.
• Batch your inputs: instead of one =COPILOT() per cell, pass a range as the context argument — for example =COPILOT("Classify this feedback", A2:A100) returns a dynamic array covering all rows from a single call.
• Convert results to static values: once you have results you're happy with, copy the cells and paste as values only. This prevents Excel from re-calling Copilot every time the workbook recalculates, which burns through your rate limit faster than you'd expect.

Other #CONNECT! errors (not rate limit)

If the #CONNECT! error shows a different reason — connectivity, service unavailable, or no specific message — check these:

• Confirm you have a working internet connection and that no firewall or VPN is blocking Microsoft's AI services
• Check Microsoft's service status page as described above
• Confirm your workbook's sensitivity label isn't set to Confidential or Highly Confidential — these labels block Copilot from accessing the file content

Copilot works on PC but not Mac (same account)

If Copilot works fine on a Windows machine with the same Microsoft account but fails on Mac, this is a known, Mac-specific desktop app issue that has affected multiple users and is tied to Excel for Mac build versions. The confirmed workarounds while Microsoft addresses it:

• Use Excel Online (office.com) — Copilot works there regardless of the Mac desktop app issue
• Clear Excel's cache: quit Excel fully, go to ~/Library/Containers/com.microsoft.Excel/Data/Library/Caches and clear the contents, then reopen Excel
• Sign out of your Microsoft account in Excel and sign back in to refresh the authentication token

The bottom line

Most Copilot-in-Excel errors fall into three buckets: Microsoft's servers having an issue (check the status page first), the Mac desktop app having a build-specific conflict (use Excel Online as a workaround), or the =COPILOT() function hitting rate limits (batch your inputs and wait). Checking service status before troubleshooting your own setup saves significant time.