HMRC notifications of VAT authority code expiry

I have just received a notification from H M Revenue and Customs that the authorisation number requested for VAT online services for a client has expired and I need to go through the authorisation process again.  I activated the authority about a month ago and have already submitted an online VAT return for the client.  I have got the submission reference etc for the return but I am concerned that something might have gone amiss at HMRC end.  Has anyone else experienced this?