判断下加载完成，再执行试试

showVideoAd(e) {
    //TODO
    rewardedVideoAd.show()
        .catch(() => {
            rewardedVideoAd.load()
                .then(() => rewardedVideoAd.show())
                .catch(err => {
                    console.log('激励视频 广告显示失败')
                })
        });
},