If your OpenAI account is more than three months old, your free credits will have expired, and it may be that you have to add some credit to your account.
Failing that, here are some debug instructions (copied from another thread):
Enable extension debug output by pasting the following command in Terminal:
defaults write com.pilotmoon.popclip EnableExtensionDebug -bool YES
then Quit and restart PopClip.
(note, substitutecom.pilotmoon.popclip-setapp
if using Setapp edition)Then open Console app and set the following filters
process: PopClip
,category: Extension
Now set Console to “Start” & “Now” you should see the API calls going in, and the responses.
Once you’ve set up the debug console, there should be some clue in the error messages from OpenAI as to the problem.