Outlook calendar

Start classic Outlook in Safe Mode and test a new appointment; if it works there, disable the COM add-in interfering with Outlook’s appointment form.

1. Test without add-ins

1. Close Outlook.
2. Press Windows key + R.
3. Enter:

      outlook.exe /safe
   

4. Select OK, choose your normal profile if prompted, and try creating an appointment.

If the warning does not appear in Safe Mode:

1. Go to File → Options → Add-ins.
2. Beside Manage, select COM Add-ins, then Go.
3. Take a screenshot of the enabled add-ins so you can restore the settings.
4. Clear every checkbox and select OK. Do not select Remove.
5. Restart Outlook normally and test an appointment.
6. Re-enable the add-ins one at a time, restarting Outlook after each, until the warning returns. Leave the responsible add-in disabled and obtain an update from its publisher.

Microsoft documents this isolation procedure for classic Outlook, including disabling rather than removing add-ins.^1^ The same procedure is the accepted resolution path for this exact appointment-form message.^2^

2. If the warning also appears in Safe Mode, clear the forms cache

Outlook keeps local copies of standard and custom forms in its forms cache. A damaged or obsolete cached form can prevent the standard appointment form from loading.^3^

1. In Outlook, open File → Options → Advanced.
2. Under Developers, select Custom Forms.
3. Select Manage Forms, then Clear Cache.
4. Close Outlook completely, reopen it, and create a test appointment.

The Custom Forms control is Outlook’s supported location for advanced form settings.^4^

If those controls are unavailable, do not make undocumented registry changes. Proceed to Office repair instead.

3. Repair Office if the form still fails

1. Close all Office applications.
2. Right-click Start:
   • Windows 11: Installed apps
   • Windows 10: Apps and Features
3. Find Microsoft 365 or Microsoft Office and select Modify.
4. Run Quick Repair first.
5. If the warning remains, return to the same location and run Online Repair. This is more comprehensive and may require signing back into Office afterward.^5^

4. If only one calendar is affected

Create a temporary Outlook profile and test that calendar:

1. Close Outlook.
2. Open Windows Control Panel → Mail → Show Profiles → Add.
3. Configure the same account in the new profile.
4. Hold Shift while starting Outlook and select the new profile.
5. Test a new appointment.

If it works, the original Outlook profile is damaged; use the new profile. Microsoft documents a new profile as the next isolation step when classic Outlook problems persist.^1^

Administrator status does not provide a safe way to force the blocked object to run. The objective is to remove the conflicting add-in or damaged forms component rather than bypass Outlook’s protection.

References

1. [Classic Outlook](https://support.microsoft.com/outlook/getstarted/outlook-for-windows-not-responding-hangs-freezes-or-stops-working)
2. error with appointment form to help prevent malicious code from running one or more objects in this form were not loaded - Microsoft Q&A
3. Understanding the Forms Cache
4. Advanced options in classic Outlook for Windows | Microsoft Support
5. Repair an Office application | Microsoft Support