Had our seats reupholstered and the back seat upper section is now straight up and down, any ideas? Did I reinstall them incorrectly? This is a convertible
Thanks!

 

I'd say you didn't install it correctly.
While not familiar with the '61 I'd have to think the top of the back is too far forward, giving you the vertical condition.
I had a '63 Impala 100 years ago and had the back seat out many times.
I maybe recall it was 'hung' from 2 brackets at the top then pushed into position at the bottom until it overcame the
resistance imposed by the rear of the bottom cushion.
I'd start my grabbing the top of the back cushion and trying to pull it towards the dash - seeing if it is correctly
'set' in its hanger.
Or something like that - sounds like a simple fix, protect that new upholstery and move slow.
Let us know what it took to make it right