The Vendor Details section and payment details are only visible and editable to users with the appropriate permissions.
Here's how an Account Owner or Administrator can grant those permissions:
Find your Organisation and open the Users page under Workflows and settings.
Click on the Permissions field next to a user.
Tick the checkboxes for the permissions you want to grant to this user.
Can view list: allows the user to see the Vendor Details section
Can add: allows the user to add payment details in the Vendor Details section or during Batch Payment creation
Can edit: allows the user to edit payment details in the Vendor Details section
Once you have made the appropriate selections, click SAVE to apply the permissions.