Co-parenting can be difficult, but it is considered the best option for a child’s welfare in the modern court room. Even if you are in a more traditional situation where one parent has sole custody, it is likely that the non-custodial parent will have the child for weekends at least occasionally. Scheduling all of this can be a challenge on its own, but if the child refuses to go and stay with one of the parents, a difficult situation often turns into a nightmare. According to Helpguide.org, if a child is refusing to go visit one of the parents, it is vital to find the cause of the refusal.
First, while it is possible that a refusal to go visit the other parent is indicative of abuse, that is not necessarily the case. It is very common for children to refuse to go visit the other parent due to more innocuous reasons such as rule disparity (maybe bedtime is earlier with the other parent), entertainment disparity (maybe there are more toys with the other parent), or maybe there is another misunderstanding. It is important to speak with the child to try and get a reason for the refusal.
In either case, it is important not to push the issue with the child and try to be supportive. Giving the child space is often helpful and may help them change their mind. A lot of refusals of this nature are temporary.
Finally, keeping communication open with your ex during this time is very important. This is likely an emotional time for everybody involved, but good communication can help you figure out what the problem is and hopefully solve it.