There are a lot of possible issues with the 2nd dataset option. It would be fastest for us to login and take a look at your installation, if possible, complete this form to provide credentials.
Or, if not possible, then use the above form to upload the failed merged PDF upload and screenshots of the following;
1 & 2. From the plugin’s EXPORT tab… Both Field Map Layouts showing the settings and at least the first row of mapped fields.
3. The plugin’s SETTINGS tab showing the “Embedded Forms” section
4. The Formidable Form’s “On Submit Message Box” showing the PRO2PDF shortcode
We remain at your service.