Question

英语高手 来帮帮忙啦~~~！！！！~~~~~~~~~~~~~~~~~~~~~~

Now, if for some reason a business plan doesn't work, try hard to discover why not, rewrite it, and immediately focus on the new plan.
这里怎么没有主语啊

Answer 1

try hard to discover why not, rewrite it, and immediately focus on the new plan.
主句属于祈使句，省略主语you.

Answer 2

这种句型叫做祈使句。
祈使句的作用是要求、请求或命令、劝告、叮嘱、建议别人做或不做一件事。
祈使句表示请求、命令、建议等等。谓语动词一律用原形。句子中通常不用主语，句末用惊叹号或者句号，用降调。 祈使句中的主语常常被省去。

Answer 3

忽略【if for some reason a business plan doesn't work,】，想想，keep quiet为什么也没有主语,这样你明白了吗

Answer 4

因为这是一个祈使句，一般一动词原形开头来（表肯定）。如：Sit down, please.