[RESOLVED] Some games and apps only had internet access when Fiddler Classic was running

Had a weird issue where some games/apps couldn't connect to online services unless Fiddler Classic was open.

For example:

• Forza Horizon would get stuck while syncing/loading my Xbox profile.
• A gacha game would fail with a generic network error during login.

Meanwhile browsers and normal internet access worked perfectly fine.

I checked:

• Windows proxy settings
• netsh winhttp show proxy
• Fiddler certificates
• Npcap

Everything looked normal.

What finally fixed it was:

netsh int ip reset
netsh winsock reset

Then reboot the PC.

netsh winhttp reset proxy did not solve it for me, but resetting the IP/Winsock stack did.

Posting this in case someone else runs into the same issue.