Hey, this is a known issue with the Prettier extension after a recent update.
There’s a workaround here: No longer eligible as formatter for many types of files · Issue #3906 · prettier/prettier-vscode · GitHub
The issue is on the Prettier VS Code plugin side (not a Cursor bug), but the workaround helps. A similar report was already closed yesterday: Prettier broke after updating Cursor to 2.39.41
Try the workaround from the GitHub issue, it should help. Let me know if it doesn’t work.