Item in Collection

I'm trying to see if a Supplier from one collection is contained in another colection. Sounds pretty simple right?

I start with a 'For Each Item in Collection' component that is full of Suppliers and then pass the 'CurrentSupplier.Sub_Number' to the 'Item Is In Collection' Item field. I'm comparing it to the SupplierPO list and have specified to lookm in the SupplierID field of that collection. It doesn't work.

On the right image you can see the CurrentDefaultSupplier.Sub_Number field and the SupplierID column from the Collection and the number is there.

Any ideas why this doesnt work?

Thanks!