When I open IDLE, it opens the window, but then shows a pop-up saying “IDLE’s subprocess didn’t make connection. Either IDLE can’t start a subprocess or personal firewall software is blocking the connection.” I tried restarting my computer (I’m running python on linux), but it still isn’t working.
https://docs.python.org/3/library/idle.html#startup-failure
What command are you giving to launch IDLE?
You might try:
python3 -m idlelib
and see if you get the same error.
I’m having the same issue as the OP when I double-click on the IDLE application in my application finder or try to open a file by right clicking it. However, I don’t have this issue when I open it with this command line instruction. Any suggestions on how to make it work with a normal “double-click” on the application?