knock for a loop

例句：

1. 1. She tried to fix the car but it kept knocking for a loop.
   她试图修好这辆车，但总是失败。
2. 2. The project kept falling apart, and they kept knocking for a loop.
   这个项目一直崩溃，他们一次又一次地失败。
3. 3.After trying everything, she finally gave up and said she couldn't do it anymore.
   经过无数次尝试，她终于放弃了，说她再也做不了了。