We apologize for the inconvenience caused, as per the description above, you are not able to access the combine pdf URL https://cloud.acrobat.com/convertpdf Is that correct?
Please try to delete cookies, temp files and reboot the machine and try to access the services. You may also access the services on a mobile device for testing purpose. Or connect the machine to a different network environment and see if this brings any difference.
Let us know how it goes.