actually it depends if you are direct customer of Qlik or via a partner.
There is Support part under Services on Qlik site. It actually points to https://qliksupport.force.com/apex/QS_Home_Page
From there you can go to Contact support and select what type of issue you have.
I can go through few selections and then I get a message that I do not have privileges to directly contact support and I should contact our partner for assistance.