Not possible to deactivate new General Ledger Accounting; see long text

What causes this issue?

The business function <LS>FI-AA, Parallel Valuation</> (<AB>
FIN_AA_PARALLEL_VAL</>) is activated.

System Response

Consequently, it is <ZH>not</> possible to deactivate new General Ledger
Accounting.

How to fix this error?

If appropriate, you first need to deactivate the business function <LS>
FI-AA, Parallel Valuation</> (<AB>FIN_AA_PARALLEL_VAL</>).
For this, see the documentation about deactivating business functions in
SAP Library under <LS>SAP ERP -> Business Functions -> Introduction:
Enhancement Packages and Business Functions -> Business Functions ->
Deactivating Business Functions</>.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.