We apologize for the inconvenience caused, as per the description above, you are getting conversion failure while converting/exporting a PDF file into Excel, is that correct?
Please try exporting the PDF file to Excel using the URL https://cloud.acrobat.com/exportpdf on a different browser like Chrome, or Firefox, or Safari and see if this brings any difference.
If possible try converting a single page PDF file to Excel and see if the issue is reproducible? Is it specific to one PDF file or happening with all PDF file?
If possible, connect the machine to a different network environment like a guest wired/wireless network, or a mobile hotspot and see if this brings any difference.
If you are using the free desktop version of Adobe Reader DC and getting the error message, please sign out and sign back in with your current Adobe ID and password from Adobe Reader and check for any pending updates from Help>Check for updates
and reboot the machine and see if this brings any difference.