How to fix the Error Excel or not functioning

Start Excel in Safe Mode; if it opens there, disable its add-ins, and if it still will not open, run an Online Repair of Microsoft 365 or Office.

1. Test Excel in Safe Mode

1. Press Windows key + R.
2. Enter:

excel /safe

3. Select OK.

Safe Mode starts Excel without most add-ins, startup files, and customizations that can interfere with startup.^1^

2. If Excel opens in Safe Mode

Disable COM add-ins:

1. In Excel, select File → Options → Add-ins.
2. At the bottom, set Manage to COM Add-ins, then select Go.
3. Clear every checkbox and select OK.
4. Close Excel and open it normally.
5. If Excel now works, enable the add-ins one at a time, restarting Excel after each one. The add-in after which the problem returns is the likely source.^1^

If necessary, repeat these steps with Manage → Excel Add-ins → Go.

3. If Excel does not open in Safe Mode

Run an Online Repair, which repairs the entire Office installation rather than Excel alone.^2^

Windows 11

1. Right-click Start → Installed apps.
2. Find Microsoft 365 or Microsoft Office.
3. Select the three dots → Modify.
4. Select Online Repair → Repair.
5. Complete the prompts, restart Windows, and test Excel.

Windows 10

1. Right-click Start → Apps and Features.
2. Select Microsoft 365 or Microsoft Office.
3. Select Modify.
4. Choose Online Repair → Repair.
5. Complete the repair, restart Windows, and test Excel.

Online Repair may require an Internet connection and can take longer than Quick Repair. For an MSI-based Office installation, choose Repair → Continue instead.^2^

If Excel still cannot start after Online Repair, record the exact message shown—including any error code—and whether Word or PowerPoint also fails. Those details are needed to distinguish an Office-wide installation problem from an Excel-specific startup failure.

References

1. Excel not responding, hangs, freezes or stops working
2. Repair an Office application