Upload file button not appearing

[Bob Gourley]

After updating to the latest version (and Wordpress to the latest version), I am no longer getting an upload button on a file upload field. When I look in the inspecter,  I see:

403 Permission Denied

You do not have permission for this request /wp-content/plugins/magic-fields-2/admin/mf_upload.php?input_name=pdf_1_1&callback=mf_file_callback_upload&type=file

Permissions for admin/mf_upload.php seem fine.

The permissions for that file do seem fine, though. Any suggestions? The site is hosted with Bluehost. Strangely, it's fine locally (running in Desktop Server, an exact copy of live site).