Dynamic dropdown returns #REF in google sheets

Question

I am creating a dynamic dropdown that returns a list of Job Orders Number that have not been completed using a =filter() formula but when using Data Validation to reference this list, it returns a #REF! as seen in the image.

I have put a sample here. Where the dropdown and list of reference is found in the tab "Work Order" and the list of reference is based on the uncompleted orders found in "Order Request".

https://docs.google.com/spreadsheets/d/1Ywy9jODh82dSyyHyRMXwhcCLmmSEbnr5rWHoMC2bkJ0/edit#gid=1852020502