Buyer versus Buyer Manager permission gaps in a live store
Key Takeaway
A user who manages other buyers' carts and orders needs the "Buyer Manager" permission set, not "Buyer". Buyer Manager requires a Customer Community Plus or higher license, so a user on an External Apps license must be upgraded.
Logged-in users of a B2B store get their access from preconfigured permission sets. Buyer is for people who shop for themselves. Buyer Manager is for people who also manage other buyers' carts, orders, contacts and reports. Each permission set requires a minimum external user license. When a user in a live store can't do what their role needs, check both the permission set and the license.
Permission sets for external users
Buyers and buyer managers are external users. A B2B store has three preconfigured permission sets for external users: Buyer, Buyer Manager, and an optional "Account Switcher". If you don't want to use the preconfigured sets as they are, Salesforce recommends cloning them and customizing the clones.
Internal users get a different setup. An internal user gets a Salesforce standard license or an Identity license (or a Sales Cloud or Service Cloud standard user license), paired with the "Commerce Admin" or "Merchandiser" permission set.