I have dig Cursor Editor errors for hours that “Cursor Tab” not available and got " Connection failed" when chat/comopser(only work for agent)，
Finally i found the reason.
It seems Cursor do not support proxy with “auto config proxy” with pac url in internet settins, remove the config,it works fine.
but i need this config to bypass firewall…
hope this finds help others and Cursor team update software asap.