Glad to see you again here in the Community, @info162.
I've got some information to share on why you're unable to link your credit card into QuickBooks Online.
Being unable to connect your credit card account in the system can be caused by the new banking regulation. It means that March 14, 2020, bank data can only be downloaded into QuickBooks through Open Banking. This allows customers to share their financial information electronically.
For those financial institutions that do not support this feature, are advised to manually import their bank transactions using CSV file uploads until the new connection is made available.
If this feature is already available on your bank, you can upgrade your bank feed connection to Open Banking. You may follow the instructions found in this link on how to accomplish this goal: Upgrade your bank feed connection to Open Banking.
Please know that our system is updating the bank feeds to comply with new Open Banking regulations.
You can check out these articles below to learn more about this process, and see what are those financial institutions that currently supports this feature: