uniapp请求接口时，一直报错401

var a_token = uni.getStorageSync('access_token');  
                    console.log(a_token);  
                    var headers={  
                        "Authorization":"bearer "+a_token,  
                        "Content-Type":"application/json"  
                    };  
                    uni.request({  
                        url: '/api/login',  
                        method: 'POST',  
                        dataType:'json',  
                        header:headers,  
                        data:{  
                            "acount":acount,  
                            "password":password  
                        },  
                        success: (res) => {  
                            console.log(res);  
                            if(res.data.success){  
                                uni.switchTab({  
                                    url: '/pages/main/main'  
                                });  
                            }  
                        },