Had this problem for a while now.....and no shop can help.
If I go to use the in-built flash I get a message on the back saying "...Menu not available. Flash is off or unsupported, or an accessory is attached..."
Now, I did have a hot shoe cover in place for a few months until that fell off somewhere in Cuba and ever since it has obviously done something to the shoe so camera thinks there is inded something attached.....next time I'll just use tape methinks!!
Have read online about cleaning shoe with isopropyl which I have done and has made no difference.....read about a small 'catch' which is pushed in when an attachment is er....attached but not quite sure what to do about it?