We have a temporary custody order in place, but my ex won't let me see my child. What should I do?
You should do the same things as if the order was permanent- file a motion for contempt immediately, and document the denial of visitation.
This is even more important when a temporary order is in effect and litigation is still in process- the visitation interference is a clear sign that the parent denying visitation will not support the relationship between the child and the other parent.
This is a factor that is considered in many States' custody statutes when deciding permanent custody orders.