Having trouble with custom date field for CPT query (WordPress)

I’ve read as many of the questions and answers on here as I can find and none of the solutions are working for me. No idea what I’m doing wrong here.

I have a CPT ‘event’ with meta key ‘start_date’ – This saves to DB in YYYY-MM-DD HH:MM:SS format exactly the same as the standard post_date format.

Yet I have a query which is not sorting these posts by the meta key but by the post_date no matter what I try.

I’ve got the actual CPT archive sorting correctly by start_date, but the query I’m using elsewhere (on homepage section) just will not work.

Here’s my query:

I’ve tried so many variations and yet it still just displays the posts by post_date rather than start_date.

Any idea what I’m doing wrong here?

Thanks