Once you resolve all error messages there, the follow up transaction creation could succeed.
2. Check the customizing for follow up transaction types in this SPRO path:
Transactions->Basic Settings->Copying control for business transactions->Define Copying Control for Transaction Types
How to resolve all task errors?
approach1: configure the necessary organization determine procedure to ensure every time the task is created, the related sales organization data could be correctly determined accordingly.
approach2: Manually fix all errors in WebUI. The reason is in My task Fiori application, there is no UI to maintain required Sales Organization related data. You have to maintain them only in WebUI.