I just bought a eos rebel sl3 with kit lens from a second-hand shop and it won't charge or turn on. The battery may have a tiny bit of rust on one of the terminals or whatever they're called and it was left in the "on" position for who knows how long. I will be receiving new batteries for it soon to see if that really is the problem but I thought I would try and contact someone to see if there are other problems with these cameras that may be causing it as well.
Hi and welcome to the forum:
When you purchased the camera, did you check to see that it worked at the time? When you purchased the camera, did you also get a battery charger with the unit - it looks like a small black box into which the battery fits and has a connection to a power outlet. If you did, put the battery on charge overnight and see if it works. If it does not work you may have to go back to the shop that sold it to you, unless they sold it 'as it' - i.e. with no warranty that it works.
When you get your new batteries, they will likely come with some charge but will need to be charged fully as soon as possible.
If you did not get a copy of the manual for this camera you can view and download it FROM THIS LINK I strongly suggest you read the manual to see how to use at least the basic operations. The instructions for charging the battery are on P35.
The shop I got it from usually doesn't accept non working electronics so I'm assuming it worked at one point. No I didn't receive a charger but that will be coming with the batteries and I can return it for full refund. It was too good of a price not to try. Especially since it's an big upgrade to my other canon camera.
Glad to know that there is some security for you. Likely the battery just went flat, in which case you will have a spare unit, which is not a bad thing. Definitely suggest you read through the manual if this is an upgrade. I have been shooting for 40 years, but I still check the manual when I get a new model unit.