Hi Mjohn,
I have looked into your account and as mentioned, you do have an active subscription for Adobe PDF Pack. So there shouldn't be any problem with conversion.
Could you confirm the process of conversion you follow? Is it through the desktop application or web browser?
If you have ever used the trial version of Adobe Acrobat DC, then you need to uninstall it first to use the PDF Pack service. As it works with the free application Adobe Reader DC only not the Acrobat DC.
Follow the steps mentioned below, to activate the subscription.
1- PDF Pack service is an online service that you can use online via: https://cloud.acrobat.com/exportpdf
2- You can also use the services through free desktop version of Adobe Acrobat Reader DC: Adobe Acrobat Reader DC Install for all versions
3- “Sign In” using the email (Adobe ID) under which you have subscription registered.
4- For detailed description of how to use the PDF Pack service, you may refer to- How to Use Adobe PDF Pack
You may refer to the following link for any troubleshooting: Troubleshooting Create PDF, Export PDF, Adobe Send, Fill & Sign … services(PDFPack or Document Cloud Services).
Let us know if it still doesn't work.
Regards,
Akanchha