@Anonymous
Can you clarify which expression you are using?
This is what I am suggesting:
less(coalesce(item()?['ExpirationDate'], addDays(utcNow(), 1)), utcNow())
If you are sure that the Expiration date is never null, then you need to check your expression for ExpirationDate. Look back at your history, output, can you see that key name "ExpirationDate". Is the spelling correct? Have you got the path correct? Without seeing your flow it is hard to comment exactly on the cause.
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.
Cheers,
Damien
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