I tried on Access 2007 and had no problem at all. I attached the file that I worked. The report is "All Assets".
First make sure that text box works horizontally. Make sure that control source is =EAN8(field), and field is indeed in the data source of the report. Security warning is disabled.
Note that I used EAN8 function. UPC_E should also work.
If you still have problems, attach your file to the reply, or you can attach it to my PM if you do not want others to see your file.

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