文件上传 - IOS 七牛7.0 上传文件报错400，不知如何解决

QNUploadOption * option = [[QNUploadOption alloc] initWithMime:@"image/png" progressHandler:nil params:nil checkCrc:NO cancellationSignal:nil];
            QNUploadManager * uploadManager = [[QNUploadManager alloc] init];
            NSString * documentDIR = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];
            [uploadManager putFile:[documentDIR stringByAppendingPathComponent: photoModel.filePath] key:response.body[@"key"] token:response.body[@"uptoken"] complete:^(QNResponseInfo *info, NSString *key, NSDictionary *resp) {
                NSLog(@"upload info : %@", info);
                NSLog(@"upload resp : %@", resp);
            } option:option];

我生成拍照文件的就是PNG图片，经由服务器获取token后，拿着去上传。【之前我也有尝试过option传nil，但也是不行】

返回值每次都是：

Printing description of info:

不知道哪里出错了