Whenever we try entering a credit card for the purchase, this message pops up:
"We weren't able to process your transaction. Please verify the billing information in your Adobe Account to continue. Once you verify this information, you can retry your purchase."
Jupiter Says Team
Go to your main Adobe account (the one you use to subscribe to Creative Cloud apps), and make sure you have a valid credit card number registered there.
Please contact Adobe customer care. Adobe customer care can be contacted by beginning a secure chat session at https://helpx.adobe.com/contact.html?rghtup=autoOpen. Pop-up blockers need to be disabled! If the chat window fails to open, or is non-responsive, use a different device to start the interaction.
Support phone numbers may be found here: https://helpx.adobe.com/contact/phone.html. Please note that phone charges may apply.
(see also here: https://community.adobe.com/t5/creative-cloud-services/how-to-contact-adobe-support/td-p/11875703 or here
Please verify the billing information in your Adobe Account.
Then you'll need to contact customer care, see Abambo's reply.