I am upgrading a 2025 project, and the preview extension is no longer working. The arrow turns but the row does not appear, and I get no javascript errors in the console.
I cannot reproduce. Note that preview row is JavaScript and it takes some time to fully load. Wait until the browser tab’s spinning icon disappear first.
You may also View HTTP Requests and Responses in Browser or try the new feature View Server-side Logs in Browser (for AJAX Requests) to check HTTP response easily.