You might try this:
Go to Settings -> System -> About phone -> tap multiple times on "Build number" until you enable "Developer options"
Then goto Developer options
Tap on Select USB configuration
Other option:
Start Xperia Companion and then connect your phone to the computer.
See if something will be initiated.
And:
open settings-> tap on magnifying glass-> type usb and try the options presented.
Last:
Try another USB cable
