HI Angeline,
You should be able to update BP attributes. However BP can be a tricky tcode - it remembers the tab you left off on the previous business partner your processed, so I recommend that you either go back to the same starting tab, or use IF logic that handles navigating to what you're changing only on the first row.
To find out what's going you
(1) You can try running in debug mode to see what is going on. You'll get a pop-up windows that you can click on as it steps thru each screen and activity (aka OK code).
(2) You can also enable extended log on the Expert Mode tab to capture additional messages and warnings

Best Regards,
Sigrid
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Sigrid Kok
PSE | Winshuttle North America
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