For existing accounts:

You should see a prompt to manually sync your panel with Remote Services. If you have not done so, perform the manual sync when you see the prompt.

The first time you log in after Partitions are enabled, Remote Services checks your account for duplicate user codes. You won’t see any visible indication of this check, but it’s a key step in configuring your account.

The next time you log in, you’ll be notified that your account is ready for you to activate Partitions.

However:

If your account has multiple users with the same user code, a popup appears, prompting the Master User (or other authorized administrator) to eliminate any duplicate user codes before proceeding.