I bought my Canon 750D brand new two weeks ago.
Worked perfect for the first week.
This weekend however I go to take a photo and I'll here the shutter click and everything. Sounds all good. I'll then go to view my picture and it'll say 'Busy... Please wait' on the screen. Then the red light on the right hand side of the camera will appear. It does NOT flash. It will just stay there.
I've turned it on and off again - still there
Recharged battery - still there
Reformatted 3 different SD cards and tried with them - still there
The only time it goes away is when there is no SD card in the slot.
I NEED HELP ASAP AS I'M A PHOTOGRAPHY STUDENT AT UNI
Try resetting the camera back to factory defaults. It is an option that appears in the menus.
Make sure your card is up to specifications. Avoid using mini-cards with adapters, which are nothing but trouble, IMHO.
If the camera and card were working fine and now are not then obviously something has changed. You've tried differnt cards and the problem still exists so in my mind that would eliminate a card failure. I think that camera has an internal, rechargeable clock battery which is not easily removable. Many times, removing the clock battery (when you can) can reset a fault. Not being able to remove that battery the other option would be to wait for it to drain completely.......which could take weeks. Not a viable option.
Unfortunately it sounds like you have exhausted the things that you can try. Have you spoken to Canon? I have spoken to Canon customer service in the past and found them to be very helpful, so that would be my next step if you haven't already. Hopefully they can be of some help to you but it may need to go back for repair.