How do I fix a Fuji "Turn off the camera and turn on again" error?

I googled the warning message – always your best first option.
The very first result, from an online Fujifilm manual, told me:

TURN OFF THE CAMERA AND TURN ON AGAIN: Camera malfunction. Turn the camera off and then on again. If the message persists, contact a FUJIFILM dealer.

So, contact a Fujifilm dealer. It looks like your camera has a more serious error that unfortunately can't be fixed easily.

The camera is showing this message because it has detected a bad state. The turning off and on can clear up temporary states but sometimes you have to go further by also removing the batter and memory card. Try again after leaving out the battery for a min or two. No need to insert the memory card as that will add another potential point of failure.

If it powers on without showing the error message after reinserting the battery, then add the memory card back to see if it causes the error. If it does, you can reformat it on most computers with a card reader or just replace it.

If it shows again the error message then the camera has a default which causes it to be in a bad state and you will have to get it serviced professionally or replace it. Always ask the price first before agreeing on the repair. For low-end products, it can cost as much to fix as getting a new one! Or at least buying a working used model.

I have a Fuji S4000 and I think I solved the problem (I am not sure if this is a definite solution). I shut off the camera and held down the on-off button for 10+ seconds.

I turn the camera on/off about a dozen times and the message hasn't come back.

Cheers! Orlando

I had the same issue with my fujifilms100x and without noticing I read this thread on another camera. I got rid of the problem by holding the off button down. It made a weird sound and I thought:"that's it, to the repair shop..." Then the error message came up again and I did the same thing.I turned it on and off and it's worked fine ever since. I imagine it's a re-setting mechanism fuji film has built into their cameras.