They say
“No one told me it was a priority.”
Your response
“Let’s look at what I actually communicated. If I didn’t make the priority and trade-offs clear, that’s mine to correct. We also need a better way for you to flag competing priorities before work is missed.”
First, check this
Did you clearly rank this work against the employee’s other commitments, or did you call it important while saying the same about everything else?
Why this works
Calling work important is not the same as ranking it against other commitments. The manager must check whether the employee received a usable priority decision. The employee also has a responsibility to raise conflicts before work is missed. This keeps the page about priority signalling; a claim that the requirements themselves changed belongs to the next conversation.
Don’t say
“It should have been obvious.”