You explicitly say “the PDF file disappears as soon as the export finishes.” How do you know that there ever was a PDF file created. What you are describing sounds like the export is failing prior to its completion and if a partial PDF file was created, it is being deleted as part of the clean-up of the failed export. Any error messages that you can see?
Have you tried exporting from a new, very simple InDesign document?
I can see a temporary PDF file on my second monitor with the file name that I gave it.
As soon as the PDF export is finished that PDF, which usually flashes and the full file appears, vanishes and doesn't display the finished PDF.
Also, there is no error message. InDesign reacts as though the export was successful.
Is this isolated to a single file, or does it happen if you make another new file?
It works with other older files but this is the one it happens to. I've even copied and pasted the contents into a new file and it still gives the same results...or lack thereof.
Does it work with NEW file that does not contain elements from this one?