Outlook 365 on PC keeps showing a missing folder error on new install, will not start

Start classic Outlook in Safe Mode; if it still produces “The set of folders cannot be opened,” create a new Outlook profile without deleting the existing one.

1. Test Outlook in Safe Mode

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

      Outlook /safe
   

3. Select OK, accept the default profile, and sign in if prompted.

If Outlook opens, an add-in is likely blocking startup:

1. Go to File > Options > Add-ins.
2. At the bottom, select COM Add-ins > Go.
3. Record which add-ins are selected, then clear their check boxes. Do not use Remove.
4. Exit Outlook and open it normally.
5. Re-enable add-ins individually until the error returns; leave the responsible add-in disabled. ^1^

2. If Safe Mode fails, create a clean profile

A new installation can still pick up an unusable Outlook profile or profile configuration. Keep the old profile until the replacement is working:

1. Hold Shift while starting Outlook. Alternatively, press Windows key + R and run:

      Outlook.exe /profiles
   

2. In the profile picker, select Options.
3. Optionally enable Prompt a profile to be used.
4. Select New.
5. Give the profile a different name, add the same email account, and complete sign-in.
6. Start Outlook and select the new profile.

If Outlook opens, set the new profile as the one to use. Do not remove the old profile yet. Removing a profile deletes its offline cached content, so first preserve any locally stored data that is not synchronized to the mail server. ^2^ ^1^

3. Reset the folder/navigation pane

If the new profile is unnecessary or the error remains, close Outlook and run:

Outlook.exe /resetnavpane

There must be a space before /resetnavpane. This removes local customizations from Outlook’s left-hand folder/navigation pane. ^1^

4. If only the old profile fails

The associated PST or OST data file may need repair. Exit Outlook completely, then run the Microsoft Inbox Repair Tool (scanpst.exe) against the affected data file. This is mainly relevant when the new profile opens successfully but the old one does not. ^1^

For a Microsoft 365 business account on Windows 10 or later, the classic Outlook startup troubleshooter in Windows Get Help can also diagnose common startup failures on the affected PC. If webmail works but every newly created desktop profile fails, the Microsoft 365 administrator should open a support case rather than repeatedly deleting profiles.

References

1. I can’t start Microsoft Outlook or receive the error “Cannot start Microsoft Outlook. Cannot open the Outlook Window” | Microsoft Support
2. Create a profile in classic Outlook for Windows