TEXTJOIN only when the condition is met?

I tried using TextJoin function with IF in it, but it somehow doesn't seem to work. I think I've written the formula correctly, but it doesn't give the solution I'm attempting to get.

Objective: I want the values from A-column to get printed out only when the values of B-column matches with the value of D-column. The intended outcome should be 1,2,3,6

Does anyone know how can I get done? Did I do something wrong? By the way, I'm using the google spreadsheet.