Hi @Zainabz, welcome to the community. I am sorry to hear about this 
It can either be a software problem or a problem related to the hardware.
If the power key is springy, but nothing happens, for example, the screen doesn't activate, the contact beneath button could be defect. However, it may also be an issue related to the software. Therefore, perform a software repair using Xperia Companion first. Note! Always back up all personal data before performing a software repair. All data in the internal memory is overwritten during a software repair. Content on an external SD card is kept. If the problem with the power key persists, contact a Sony Mobile repair partner to have the smartphone or tablet examined, and get a quotation for a repair.
If the power key isn't responding, feels dead and isn't springy, it is most likely a hardware problem. Contact a your Local support to have the devices assessed.
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