Is anyone having an issue with Combining Files. I can't seem to my system to complete this operation.
We apologize for the inconvenience caused, as per the description above, you are not able to combine PDF files, Is that correct?
Try combining the PDF files with the URL https://cloud.acrobat.com/combinepdf with your Adobe ID and password on a browser like Chrome, or Firefox, or Safari and see if this brings any difference.
The record shows that you are subscribed to Adobe Acrobat Pro DC license, check for any pending updates of Acrobat from help>check for updates, restart the machine after installing the updates.
Try repairing the installation files in Acrobat from help>check for updates, restart the machine and see if this brings any difference.
If the issue persists, please use Acrobat cleaner tool to remove Acrobat Download Adobe Reader and Acrobat Cleaner Tool - Adobe Labs
Reboot the machine and install Acrobat from Download Pro or Standard versions of Acrobat DC | Non-subscription
Let us know how it goes.