The Quicken Error CC-506 mainly occurs due to some issues from the side of the financial institution. Some of the most common reasons are when the financial institution account has been shut down. It might even occur if the account number is changed on the financial institution's website. However, a few more common reasons are the corrupt registry, malware attack, or improper installation of the software. This issue should fix if you update Quicken, or refresh the account details. Also, you can try deactivating and then reactivating your account.