Latch to lock and unlock window does not stay down and locked anymore it pops up

Hello,

Thanks for your post! The faceplate from your lock is similar to the 38-036 Rear Mount Casement Lock. To determine if this is the correct match, you'll need to carefully review and compare the dimensions. 

This part is not sold with screws, so you'll need to reuse the existing screws for the installation.

Alternate view of 38-036