We apologize for the inconvenience caused, as per the description above, you are not able to use the Adobe PDFPack subscription to edit a PDF file, Is that correct?
With Adobe PDFPack, you can easily create, combine, sign, and send PDF files online. You can also convert PDF files into editable Word or Excel files.
You cannot edit PDF files with Adobe PDF Pack. You need Acrobat DC to edit PDF files. See Adobe Acrobat Pro DC: PDF converter, convert PDFs from anywhere.
You can use the Adobe PDFPack services through the URL https://cloud.acrobat.com/convertpdf with your Adobe ID and password on a browser like Chrome, or Firefox, or Safari.
You can also use the free desktop version of Adobe Reader DC to use the services of Adobe PDFPack, just "sign-in" with your current Adobe ID and password in Adobe Reader DC. To download Adobe Reader https://get.adobe.com/reader/enterprise/
For troubleshooting, you can refer to Troubleshooting Create PDF, Export PDF, Adobe Send, Fill & Sign … services(PDFPack or Document Cloud...
Feel free to update this discussion for any further assistance.