Cannot complete your purchase

Question

Whether purchase inApp or at AppStore, it just spawn a dialog and says "Cannot complete your purchase..."
The purchase functioned well last week but cannot work today. I changed my VISA to another one and it still don't work.
Please help me to fix the purchase function as soon as possible.

Answer 1

If you have more than one user account, these instructions must be carried out as an administrator.
Launch the Console application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Console in the icon grid.
Select "/var/log/install.log" from the file list. Post the messages from the last installation or update attempt, starting from the time when you initiated it. If you're not sure when that was, start over and note the time.
Post the log text, please, not a screenshot. If there are runs of repeated messages, post only one example of each. Don’t post many repetitions of the same message.
When posting a log extract, be selective. Don't post more than is requested.
Please do not indiscriminately dump thousands of lines from the log into a message.
Important: Some private information, such as your name, may appear in the log. Edit it out by search-and-replace in a text editor before posting.