Updating the Accounts in the Business Purpose: Bill To Section

Hello,

Many Customers have been converted and we noticed an issue with the Accounts in the Business Purpose: Bill To Section where the Receivables, Revenue, Tax Freight etc Account Code Combinations are defined. None of the account code combinations have the Business Unit filled in. We tried to enter the Business Unit(BU) manually and even that could not be done. I have tried using the MOAC responsibility and I have tried using specific OU Responsibility; also created Customers manually and then tried to enter BU in the Account Code Combination but we are facing the same issue - when we query