We have a pretty standard living room set up with a TV sitting on a not-that-high cabinet which is easily in reach of our seventeen month old. Our apartment is very small and for that reason we're not able to put the TV in a less accessible location (wall mounting is also not an option).
We're happy to let our toddler walk around the place and explore and generally have a tolerance for her making a mess of things and getting into things that she shouldn't. However, recently she's picked up a bad habit of walking up to the TV and hitting it as hard as she can and pushing it as far towards the wall as it will go. We understand that it's natural for her to want to touch and play with anything she can but her hitting the TV like this is obviously problematic - not just because she might break the TV (which would be a tragedy of course) but also because we're worried that it could fall on top of her and hurt her.
Over the last few months we've made a real effort to teach her the word 'no' by gently grabbing her and restraining her when she's doing something she shouldn't and repeating the word clearly a few times. This worked for a while and she was really responding and there was a month or so where we could just say 'no' to her and she would stop whatever she was doing and not be terribly upset about it. Over the last week or two though she's stopped responding to 'no' - I don't think it's that she's forgotten what it means but rather that she's growing to be a more stubborn toddler and just resisting. Earlier my wife was even holding one of her hands and saying no to stop her hitting the TV and my daughter just ignored her and kept pushing the TV with her free hand.
She has a play pen that can keep her from getting around the whole place but we don't like to keep her in there too long - partly because she gets very impatient and bored if we leave her in there for more than an hour or so but also because we think it's good for her to be able to explore around the entire apartment, too. We have tried a method of gentle 'punishment' where we pick her up and put her down in the pen every time she touches the TV hoping that this will discourage her from going near it but it doesn't seem to have changed her behaviour.
Does anybody have any suggestions for tips we can use? The ideal solution would be to get her to respond properly to the word 'no' again (she has some other habits that we'd like to curb too like pulling books out of our bookshelf or opening drawers and pulling clothes out but the TV issue is by far the most pressing) but if there are any other ideas then I would be very happy to hear them.