While in Reader, when I try to export to Excel, it asks for login info. It doesn't take my username and password via the Adobe reader app. Doesn't recognize it. However, when I go to Adobe.com, I can log in with the same credentials with no issues and confirm that I have the annual PDF Convert subscription.
Make sure that you are "Signing In" using the correct email address under which you have made the purchase and you have installed the correct application "Adobe Acrobat Reader DC" not the "Adobe Acrobat DC"