See attendant

One day, while swiping my Oyster card on the reader at a tube station I got the “See attendant” message. The gate remained open.
Am I
A) supposed to go through and ignore the message
B) go through and then find the attendant
C) not go through and back out of the line and find the attendant?
How will this affect “don’t touch in and you will pay the maximum fare”?
In the course of events I backed out and the attendent told me to go through and ignore the message. I have no clue as to whether I was charged £1.50 or £4.00 for the journey.