Trending @Accenture; Received transport invoice mail asking for valid wbse

In the mail it's mentioned that February month transport costings are prepared by mid of April as they have some dependency from the operation teams now they are seeing that for the July month the wbse is invalid so why the month of July that project got over and now I am in a new project where transportation is not needed so what shall I do what shall I say in the mail because project is bound to keep the wbse open until or else should be able to use alternative wbse and it should be kept open around 90 days but my project got over by the month of July it is not valid anymore and there asking to give a valid wbse so that I don't fall under the gating issue what does that mean what is gating issue