Use a dynpro greater than or equal to 9000

What causes this issue?

You attempted to assign an invalid screen number.
Screen numbers between 0001 and 8499 are for SAP applications; those
between 8500 and 8999 are for SAP Partner developments, and those
between 9000 and 9999 are for customers' own developments.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Please support development by customers and SAP Partners

Error message extract from SAP system. Copyright SAP SE.