PDFMaker Mail Merge in MS Word failing to email documents

Hi there, 

After much searching through these forums and all over google I still have not come to a conclusion of this issue. 

We are seeing an error occur during a mail merge usign PDF Maker. 

• Using Word Desktop App - MS E3 license
• Using Adobe Acrobat Pro DC 

My colleague can go through a Word mail merge process and then go to Merge to Adobe PDF to create the PDF and mail them to the recipients based off an email address in the merge data set. At this point we get an error pop up as below:

There is absolutely nothing wrong with the spreadsheet containing the data, as I am able to run the exact same process on my version. The difference that I have is:

• I have Adobe CC (including Acrobat Pro)
• I am on a MS Business Premium

My colleague was previously able to generate the PDFs and email them correctly when she was logged in with the Adobe CC license that is available in the office (we have had to change this process as we need more users to use the service) and her E3 license. 

I am at my wits end about why this is not working, I cannot seem to find any reason why it cannot read the emails correctly and finish the merge.

Any help appreciated

Thanks

Nick