In late December, Barcelona's appeal to the Court of Arbitration for Sport was unsuccessful and the original transfer ban was reinstated, leaving the club unable to utilise the 2015 winter and summer transfer windows. On 5 January 2015, Zubizareta was sacked by the board after 4 years as director of football. The next month, Barcelona announced the formation of a new Football Area Technical Commission, made up of vice-president Jordi Mestre, board member Javier Bordas, Carles Rexach and Ariedo Braida.

Answer this question, if possible (if impossible, reply "unanswerable"): During what year was Barcelona not allowed to use  their transfer windows?
2015