Warning: Instance created by `useForm` is not connect to any Form element

Before Modal opens, children elements do not exist in the view. You can set forceRender on Modal to pre-render its children. source

  <Modal forceRender visible={visible} onOk={okHandler} onCancel={closeHandler}>
    <Form form={form}>
      <Form.Item name="user">
        <Input />
      </Form.Item>
    </Form>
  </Modal>