asleep at the switch
not paying attention.
Health experts were asleep at the switch when the disease began to spread rapidly again.

Etymology: based on the idea of someone going to sleep while they are responsible for operating the switch (= device) that allows a train to move from one track to another

[TahlilGaran] English Idioms Dictionary ▲

asleep at the switch
to not be alert to an opportunity
I think I was asleep at the switch. I did not know that the job was available so I never applied for it.

[TahlilGaran] English Idioms Dictionary ▲

asleep at the switch
adj. phr.
1. Asleep when it is one's duty to move a railroad switch for cars to go on the right track.
The new man was asleep at the switch and the two trains crashed.
2. informal Failing to act promptly as expected, not alert to an opportunity.
When the ducks flew over, the boy was asleep at the switch and missed his shot.

[TahlilGaran] English Idioms Dictionary ▲