Pushing fails. Mindex uses the credentials your machine already has, so the fix is usually outside the app.
Mindex does not store Git credentials. It uses whatever your machine is already set up with, which means a push that fails here will fail in a terminal too — and that is the fastest way to see the real error:
git push
GitHub no longer accepts account passwords. Use a personal access token as the password, and let your credential helper remember it:
git config --global credential.helper osxkeychain # macOS
git config --global credential.helper manager # Windows
git config --global credential.helper store # Linux
Check the key is loaded and the host recognises it:
ssh -T git@github.com
If that fails, add the key:
ssh-add ~/.ssh/id_ed25519
git remote -v
An HTTPS remote will ask for a token; an SSH remote will ask for a key. Mixing up which one you have set up is the most common cause.
If the push reports everything is up to date, the commit did not happen. Check that the changes were staged and committed first.