Someone else is logged in cant activate my account

Ive recently purchased a ddj-rb and installed rekordbox, but when I want to activate my activation key it tells me that my friends account is still active. Some time ago I went to my friends house to try his ddj-rzx, we installed rekordbox on my computer but didn't activate any licence. I deleted rekordbox off my computer afterwards since I didn't see the utility at the time because I didn't have any controllers. But now I cant change my friends account and I cant activate rekordbox DJ with my account and my activation key.

Please Help! 

Thanks