The net file the Larian launcher points you to is the wrong one, you need to download the installer
Thread 'how to get BG3 Patch 9 to work after updating'
https://windowsforum.com/threads/how-to-get-bg3-patch-9-to-work-after-updating.263501/Or the other option is to verify Bg3 which should download a new Larian launcher that doesn't look for the net file
