I don't know, maybe I don't download enough or the right things, but everything I try comes fine and quickly, even with using AV1.
People could try H264.
Maybe try, before doing a clean uninstall, delete everything in the temp folder with SF closed. Then try again.
Open File Explorer in Windows and paste in (code) from below, and you will see(screenshot below), and then select all and delete.
Screenshot

%HOMEPATH%\Documents\DVDFab\StreamFab\Temp
ADDED: Using a VPN can and will affect SF performance and may cause it not to analyze or download at all.
If using a VPN, try different VPN servers, if possible different locations, and even a different VPN provider if possible.
Also, if 6226 works, then keep that and 6228, soon to be 6229. The only change for Netflix recently was in 6227 ...- Fix: A problem that videos cannot be downloaded in AV1/VP9 video format when set to AAC audio from Netflix.