过去完成进行时是英语中一个比较复杂的时态，表示过去某一时刻开始，一直持续到过去的另一时刻的动作或状态。过去完成进行时的否定句形式为：had not been + 现在分词。
以下是一些过去完成进行时否定句的例句：
- I had not been studying English for very long when I moved to the United States.（我搬到美国时，我还没有学英语很长时间。）
- They had not been working on the project for more than an hour before they realized they were going in the wrong direction.（他们还没工作一个小时就意识到他们走错了方向。）
- She had not been practicing the piano much lately, so she was nervous to perform in front of the audience.（她最近没怎么练钢琴，所以在观众面前表演时很紧张。）
- The team had not been playing well all season, and it was no surprise when they lost the championship game.（整个赛季，这个团队表现都很糟糕，他们输掉了冠军赛也不出人意料。）
- He had not been paying attention in class, so he didn't understand the homework assignment.（他上课没认真听讲，所以不理解作业。）
以上是一些常见的过去完成进行时否定句例句，希望能帮助大家更好地理解这个时态。记住，过去完成进行时是用来描述过去某一段时间内的动作或状态，否定句的形式为had not been + 现在分词。
