Error with Shared Links Setting

please help

Hi Rong, 

Welcome to the Box Community!

It looks like you are trying to change the "Default Permission" when creating a new shared link on contents you own and as I have checked, this settings in unchangeable for users that are on Personal plan. Although this specific setting is fixed, you can still change the access type when you generate a shared link. You should still be able to allow users to Preview and download your content by changing the link access to "People with the link" and enable the "Allow download" in the link settings.

To learn more about Shared links permissions and link settings, please check out these articles:

• Creating Shared Links
• Individual Shared Link Settings

Thanks for your post and let us know if you have any questions!