App({
  onLaunch: function () {
    console.log('执行')
    wx.loadFontFace({
      family: 'DIN',
      source: 'url("https://kupiwang.oss-cn-hangzhou.aliyuncs.com/font/DIN%20Medium.ttf")',
      success(res){
        console.log('res', res)
      },
      fail(err){
        console.log('err', err)
      },
      complete(res){
        console.log('complete', res)
      }
    })
  }
})

真机上没有效果也不执行回调

开发者工具没有问题

代码片段：https://developers.weixin.qq.com/s/1PC3PZmK7El7