This is what i saw in the letter...
I am writing you today to tell you there has been administrative error,you were sent a letter yesterday indicating you are invited to attend your citizenship ceremony.
However all clients must have valid clearances before they are able to take the oath of citizenship.
You were scheduled before your clearance came through.We will reschedule you for another ceremony once all clearances are valid. I apologia for this administrative error and any inconvenience it may have caused.