Share your experience!
So my phone is only a few months old. A few weeks ago the auto-rotate stopped working for a while, but it fixed itself so I ignored the issue.
However, it's back. This time, it's been like this for 3 days and the problem isn't getting fixed. I've tried:
Turning Auto-Rotate on/off
Hard resetting the phone (volume key + power button)
Factory Resetting the phone
Restarting the phone with auto-rotate on/off
To no avail. Now:
Don't tell me to download a third party app, I refuse. There were no updates involved before the issue started. The gyro sensor works - when I use the camera the controls rotate as needed - the problem only exists in things like WhatsApp (or anywhere I have to use the keyboard), the Album, etc. It is a huge issue for me as I use my phone a lot for photo viewing and texting, and the keyboard is too small for me to use in Portrait mode.
Please, any help? Sending the phone in to my service provider is a mess as they don't give loan phones and sometimes they keep the thing for up to 6 weeks. Anything else I can try? I'm starting to become incredibly disappointed in Sony. If this problem extends to my Xperia Tablet Z as well I'll be very, very disappointed indeed!
I had the exact same issue... big fingers and all 
i went through all the diagnostic tests that the phone has and everything was working, i didn't want to resent it to factory settings and lose everything, so i opted out of trying it.
after just about giving up... i changed the phone to the basic home screen, then switched the auto rotate off then back on. i then immediately restarted the phone, letting it set on the table without moving it while it turned off and then back on. i let it set there a few min while i prepared to be disappointed... but when i picked it back up, to my amazement it it worked!
idk if this solution will work for everyone. maybe if someone else tries it they can post a reply as to whether it worked for them.
You are brilliant! This worked for me too! Thank you so much for giving the solution to a problem that has been bugging me for ages!
Good day!
I would like to ask for assistance for my Xperia C4. On the first day, the auto rotation and other services are working well. However, after 2 hours, the auto-rotation suddenly stops. I've tried to check the settings & reboot the unit many times for several days. I even tried to reset factory settings but no change at all. Please help me what to do and I am really hoping that you could help me. Thank you and God bless you!