After playing around with it I realize, like you said, that it wasn't the file path that caused the error. Im trying to reference a closed workbook with the function INDIRECT. Basically I want to use a formula similar to this one:

INDIRECT("'"&$A$2&"'!"&B3)

This references a specific worksheet whose name is in cell A2.

I instead would like to reference a closed workbook whose path is in A2. Is there anyway to do this?