I’ve seen this happen a few times while converting MSG files to PDF. The main reason is usually the way the tool reads the MSG structure. Some converters don’t fully capture attachments, especially if the file has embedded or uncommon attachment types.
In my case, a few PDFs were created fine, but the attachments just didn’t show up or were saved separately. I later discovered that my software had issues with processing MSG attachments. Another possibility here is that either your file may be slightly corrupt or your attachment is too big for embedding into the resulting PDF document.
It was very helpful for me to use another conversion software called Softaken MSG to PDF Converter, which leaves your attachments in a separate folder while you are converting documents.
Make sure to test it on a few files first just to see whether it works for you or not.
