Trouble shooting#NA error in Array formula

I'm receiving a #NA in a array formula that I have used successfully on a
weekly basis for the past 2 years. Today, however, I'm receiving the #NA
error.
I have a work*** named "Data" that hold my source data. I named two ranges
called "vendor" and value in this work***. I have another work*** that
has the array formula "={sum((vendor=Acer)*(value))}". For some reason I'm
getting #NA today and have no idea why. Can anyone help me solve this
problem?
Thanks,
Perplexed in Miami
.