What are you doing wrong? You are not searching for answers.
Check the machine is emptying
Check the pump & filter if necessary
See this, which I found in a ll of 60 seconds:
http://www.diynot.com/diy/threads/hoover-performa-900-ac90-001.10797/
http://www.justanswer.com/uk-appliance/4z35j-hoover-performa-1100-wouldn-t-open-programme-ended.html#re.v/491/
http://www.fixya.com/support/t12174854-hoover_performa_900_washing_machine#solution-section
XXX, February 2016