You are entering transactions and your company's address is being replaced with the customer's ship-to address as the origin. Transactions on the AvaTax Admin Console show your customer's ship-to address as both the source and destination. You have location codes disabled.
The addressee field in your subsidiary settings must have an entry for your company's name.
Navigate to Setup > Company > Subsidiaries > Click "View" > Click "Edit" on the first address.
Enter your company's name as the Addressee and save the record.