My Nested IF Function is failing, but why?

I have done a lot of research on this but i am struggling to find the answer due to each question being specific to their data.

I have a nested IF function, where i would like it to change the cell value to either "Completed" or "Not Completed" depending on a few criteria.

Firstly, the function looks through the Data and then sees if the cell value matches a value in the data, then if true, looks at the next value and if there is a match, it then goes through the corresponding matches and sees if all values are set to delivered. If they are all delivered, the cell should change to "Completed", and if not "Not Completed".

Below is the function i have, that currently fails on the first IF.

{=IF('Sub Tasks'!J:J=A2,IF('Sub Tasks'!K:K=B2,IF('Sub Tasks'!AA:AA="Delivered","Completed","Not Completed"),"NOT TRUE1"),"NOT TRUE2")}

There are also screenshots of the test i am running.

OutputSheet OriginalData