应该是They didn't stop the work until two o'clock
not until &until 的区别:
not until意思是:直到.才(瞬间动词)
until意思是:一直(持续这个动作,持续动词)...
For example:
I didn't go to bed until 10:00
我直到10点才睡觉
I work until 10:00
我一直工作到10点.
I'm just 14/15