Named ranges/functions formula trouble with Google Sheets

Hello All,​

I am currently working on a project for my portfolio, below is the info I have been given. I am having trouble getting my formulas to work.​

Your Task​

The dataset to the right contains the Titanic data that you have worked with before. In cell G2 there is a function that will generate a list of unique last names. Study this function to understand how it works. Once you understand how the function operates, create a named function called UNIQUE_LAST_NAMES with a single parameter full_name_range to replace the function currently in cell G2.

Once you have created the custom named function, clear the contents of cell G2 and use the function UNIQUE_LAST_NAMES to regenerate the list of unique last names.

* current function provided in cell G2 =UNIQUE(ARRAYFORMULA(IFERROR(LEFT(A2:A,FIND(",",A2:A)-1),LEFT(A2:A,FIND(" ",A2:A)-1))))
* I have named A2:A1314 "full_name" It is from sheet Titanic

*FULL_NAME_RANGE - current formula to extract the last name only from Column A - =LEFT(full_name,FIND(",",full_name)-1)
formula used without full_name - =LEFT(A2:A,FIND(",",A2:A)-1)
I have tested both of the above formulas and they work on their own
* Named function UNIQUE_LAST_NAMES - =UNIQUE(ARRAYFORMULA(IFERROR(LEFT(full_name,FIND(",",full_name)-1),LEFT(full_name,FIND(" ",full_name)-1))))


Below is a small snip from the sheet as it contains 1315 rows.



any help with this is greatly appreciated as I am not sure exactly where I've gone wrong, and have been messing with it for far too long.