Hello AHK,

Thanks for reaching out! Checked in with our Sage 50 CA product manager who advised that you'd need to create a new Sage ID, it's not possible to modify the username currently used. 

Step 1 would be to stop sharing your company file.

Step 2: Set up Sage Drive again using the new Sage ID tied to your newer email address, for this see:

Thank you, Erzsi.