Can someone tell me why an SQL formula with one field will work but one with 2 fields will not?

I'm attaching 3 screen shots. Are we not allowed to add 2 fields to an SQL Formula to create a link for a virtual field?

This works

This does not work, but I need to grab the InternalID and the FileName to access the correct link to the file.

This is my blob adapter configuration for Internal Applicants Controller

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