Have had the same issue since release on my Mac. I kept rolling back to previous version, but eventually it would automatically update to cursor 3 even though I kept clicking “Later” on the update popup. Accidentally found a fix that has worked: When opening Cursor on a ipynb editor, I would get the issue. While ipynb is loading (forever), switch to another file (I opened a sql file, which opened correctly). With the editor on the sql tab, I quit cursor (cmd+Q), reopen, and then everything loaded perfectly.
I did some tests and it’s easy to reproduce. It seems like, when starting Cursor directly on a ipynb file, the IDE doesn’t load properly (not even terminal). when starting on another kind of file, it loads properly and you can access your ipynb files afterwards