To some extent this depends on why the child is in music. In general, I prefer not to force my children to do any one thing - if they don't like music, then that's fine, don't do it. They have to do something physical, and something mental, but there's no one requirement - they can change if they don't find they like something.
In my childrens' cases (both around your child's age), though, both do enjoy music, and both like to play; but of course, neither likes practice all of the time. It's very important to not force practice when it's not happening that day; there's no better way to make a child dislike music (or playing their instrument) than to force them to practice when they're really not feeling it. But, it's not reasonable to allow them to never practice, of course.
For us, since our children choose to play music, the higher level is simply to tell them that if they choose to continue playing music, they must practice; it wastes our money, and (since we're in Suzuki) my time, for them to go to lessons and then not practice. So if they're on a no-practice kick for an extended period of time, we set up a chart, and say you must have some number of practices in this period, or we'll take a break from lessons.
Beyond that, we do a few things to help them choose to practice. This differs by the kid - what works for one does not work for the other, and so you have to consider your individual child. My oldest is very externally motivated, and loves having goals that he can achieve. What works for him is: he comes home from school, and has a list of things he must do before he gets to play with his friends. One of those things, is music practice. When he's done, he gets screen time based on what he did - some time for going to school, some time for practice, some time for homework. This gives him the self-motivation to do it by himself.
For our youngest, this doesn't work. He isn't driven by external motivating factors, and isn't interested in goals; he has to want to practice. So in his case, we do what we can to make practice fun. Very important for the younger sibling in my experience is to have some sense of control (as often younger siblings feel less in control, in part due to the older sibling relationship and in part due to seeing the older one have more freedom). So, we set up a list of things for the practice, and let him decide what we're going to do. The teacher offers maybe five or six things to work on.
Then, since he's internally motivated to improve, we also focus on helping him see how the practice is helping him improve. That can be super hard to see as a child - heck, as an adult - and so we set him very small musically-focused goals to help him see what he's achieving. If he's learning a song, maybe it has an ABCCB pattern, then learning each of A,B,C is a goal, separately; and when he achieves that, we celebrate (maybe just a high-five). Since he's internally motivated, he gets excited about this, so it works well for him.
The important part for both, but in particular for our youngest, is not to force the practice, though. When we've tried pushing harder on that, it snowballs - he dreads practice so it's even harder to get him to choose to do it. So what I'd do in your case is back off for a bit - a few weeks, maybe - and reset. Then try some of the above, slowly reintroducing practice in a positive way that either directly encourages your child to choose to practice, or helps them see the benefits. See if your child does some practices on their own in that time - and if not, that's okay, just give some space.
