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It's quite easy for me to answer this question, your phone is water damaged. I used to have Sony Xperia Z and which was water damaged too, I couldn't pull down the notification/illumination bar. The water entered through your speaker at the top which happened to me. It's quite notable that you'll have to spend like half of the price of your phone to fix this issue...but I have something easy round for you. You should place that phone in a polythene bag for 3 days minimum with full of dried rice and every path ways that water can enter should be opened up. 'Cause mostly water damaged phones are fixed by rice because rice s-u-cks every water out of your phone.
Note: Now I'm SP user. Had to sell that old phone after fixing the issue.
Hit Kudo if I helped you.