Thank you for reaching out to Canon USA!
Here in the US, the EOS 1200D is known as the EOS Rebel T5. Usually when the camera refuses to take a photo and it beeps and a light flashes in the viewfinder, that indicates the camera is unable to lock focus.
One thing that you can try, if you're using the EF-S 18-55mm lens that came with your camera, is to change the focus switch on the side of the lens from AF to MF, then twist the focus ring on the front of the lens (not the zoom ring) from one side to the other. You may feel a little resistance. That is OK, however, you don't want to force anything. You might also hear a slight pop or click. That's OK, too. Again, don't force anything.
Once you've completed that, put the lens back in AF mode, put the camera in P mode on the top dial, ensure the flash is down, and try to take a photo in a well-lit place.
If this doesn't work, you'll want to get in touch with technical support for further assistance. Support here in the USA or in Canada can be reached at 1-800-OK-CANON (800-652-2666). If you're outside of the USA, you'll want to click HERE and select your region/country for your support options.
We hope this helps!