You’ve got an iPhone and a Windows PC, calendar entries made on one aren’t reaching the
other, and nothing reports an error. This combination breaks quietly and often.

How it’s supposed to work

Outlook on Windows doesn’t talk to iCloud natively. Apple provides iCloud for Windows,
which installs an add-in that creates a separate iCloud data file inside Outlook. Your iCloud
calendar and contacts live in that file — not in your Outlook account’s own calendar.

That distinction explains most of the confusion. If you create an appointment in the wrong
calendar, it will never sync, because it isn’t in the iCloud one.

Work through these in order

1. Confirm which calendar you’re actually writing to

In Outlook’s calendar view, the left panel lists your calendars grouped by account. There
will be one under iCloud. Anything created in your Outlook or Exchange calendar stays there.
Make the iCloud calendar the default if that’s the one you want your phone to see.

2. Check the add-in is still enabled

Outlook disables add-ins that it thinks are slowing startup, and it does this silently. Go
to File, Options, Add-ins. If the iCloud add-in is listed under Disabled Application Add-ins,
re-enable it — and in the “Manage” dropdown choose “Disabled Items” as well, since Outlook
keeps two separate lists.

3. Sign out and back into iCloud for Windows

Open iCloud for Windows, untick Mail, Contacts, Calendars and Tasks, apply, then tick it
again and apply. This rebuilds the connection and clears a surprising number of faults.

4. Check for two-factor and an app-specific password

If your Apple account uses two-factor authentication — and it should — some configurations
need an app-specific password generated from your Apple account page rather than your normal
password. A sync that silently does nothing is a common symptom of this.

5. Look at the data file

File, Account Settings, Data Files. There should be an iCloud entry. If it’s missing, the
add-in isn’t properly installed, and a clean reinstall of iCloud for Windows is faster than
troubleshooting further.

When the versions don’t match

New Outlook and the classic Outlook behave differently here, and the iCloud add-in has
historically supported classic Outlook. If you’ve recently been moved to the new Outlook and
sync stopped at the same time, that timing is the cause. Switching back to classic Outlook is
usually possible with a toggle in the top corner.

The alternative worth considering

If this keeps breaking, subscribing to your iCloud calendar as a read-only internet calendar
is more stable — you lose the ability to edit from Outlook, but it simply keeps working. For
many people that’s the better trade, especially if the phone is where appointments actually
get created.

If you’d rather not spend an evening on it, we untangle Apple-and-Windows setups for
Canberra clients regularly — 02 6188 9898.