Acct. & for trans./event key &, postable directly

What causes this issue?

The stock account determined automatically by the system is one that is
directly postable. However, this stock posting can only be made to an
automatically postable account.

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?

INCLUDE NA_SYSADMIN1

Error message extract from SAP system. Copyright SAP SE.