Hello, please try the following: 

1. Exit/Shut down the Sage 50 instance
2. Rename the file “APIACCSS.DAT” in the affected company data folder to a different name (e.g., for a sample company it would be in “C:\sage\Peachtree\Company\Sample\PTXA\BCS”)
3. Restart Sage 50 and the application

Sage 50 will create a new DAT file and prompt for authorization when the application tries to connect.

Thanks!