Hello Nathans,
We apologize for the inconvenience caused, as per the description above, you are not able to combine PDF files and it's asking you to resubscribe for the services, Is that correct?
The record shows that you are subscribed to Acrobat Pro DC subscription with your current Adobe ID, you can try combining the PDF files through the URL https://cloud.acrobat.com/combinepdf with your Adobe ID and password on a browser like Chrome, or Firefox, or Safari.
In Acrobat Pro DC, please sign out and sign back in with your current Adobe ID, and check for any pending updates from help>check for updates. Reboot the machine and then try combining the PDF files.
For more troubleshooting, you can refer to Troubleshooting Create PDF, Export PDF, Adobe Send, Fill & Sign … services(PDFPack or Document Cloud Services).
Let us know how it goes and share your findings.
Regards,
Anand Sri.