Since you can sign in to your Apple Account elsewhere but iTunes is giving connection errors like -50 and 9309, I wouldn’t keep changing your password.
Apple’s System Status currently shows the services operating normally, so I’d check the PC itself first. Make sure Windows has the correct date, time, and time zone, and temporarily check whether antivirus, firewall, VPN, or other security software is blocking iTunes from reaching Apple’s servers.
Also make sure you’re running the latest iTunes version available for Windows.
If this only started last night and Apple Support has already walked you through the usual account and network checks, I’d avoid reinstalling or making major changes for now. The exact error numbers and the fact that purchases and purchased music are both affected are useful details to give Apple if it continues.