Answer: Inflexibility.
Explanation:
Inflexibility is a state of being unable to adapt to a new situation or a change that occurs.
In this case, the organizers of the concert are, despite the growing interest for the event, unable to increase the number of seats available. This is probably because of the limited capacity of a hall/arena where the concert is held. The organizers, however, should come up with an alternative solution. If a large number of fans is interested to buy tickets, they should schedule another concert of the same performer. If fans are turned away, they feel disappointed, and thus the interest for a particular performer drops.
