Be sure there are no other test, abandoned or failing field map layouts for the same form that are set to send PDF attachments. If there are none and the issue remains, let us know if the export button on the EXPORT tab is exporting PDFs correctly.
After checking the above, complete this form is you want us to take a look at your installation.
Thanks. Seems the problem is solved.
Just did a tidy up of unused forms and templates and also any field map layouts that were not being used.
Not sure which one had caused the issue. I need to mention that I had a form and a template with the same name. I also deleted all the demo data that came with this plugin.
For anyone who is wondering, to delete a field map layout, load it up and then scroll to the bottom and hit “Delete Entire Field Map”. (It may be obvious, but it took me a few minutes to figure that one out)