Maintaining accounts related to partner is mandatory in Odoo as these are often used to initiate the purchase and purchase return processes in Odoo. Make sure when you update the accounts they are correct and of following these ground rules. Such as Accounts payable/AP needs to be of internal type as payable and with reconciliation feature and importantly account type as Payable.

Accounts receivable needs to be of internal type and account type as receivable and reconciliation.

Use below screenshot to do the changes at odoo. Navigation Purchases>>Purchase>> Suppliers>>Accounting tab-