This error appears when the buffer stock feature is not activated at company level.
Action required from your end
Step1: Navigate to Configurations> Customers> All
Step2: Click on Company Configuration which is the third gear icon action button under action column.
Step3: Check the Enable Buffer Stock and update the settings by clicking the Save button
We hope the details above were helpful for you. Please feel free to share with us if require further assistance and will be happy to take it up.