Error When Creating/Modifying an Office 365 Account

Symptom:

An error that resembles the following messages occurs when I create/modify an Office 365 account and assign one or more attributes of mailbox:

[… Failed to modify account mailbox attributes because account’s mailbox does not exist …]

[… Failed to modify account mailbox attributes because account is not licensed …]

Solution:

Mailbox attributes cannot be set without the existence of the account’s mailbox. The error might be due to one of the following reasons:

No Exchange Online license is assigned to the Office 365 account
The mailbox creation is still in progress
There is an error on Exchange Online license assignment or the mailbox creation.

In order to rectify the issue, follow one of the steps below:

Assign the Exchange Online license to the account, if not already assigned.
Wait until the license option status has changed from PendingInput to Success, before proceeding to setting up the mailbox attributes
Contact Microsoft regarding the license assignment or mailbox creation failure.