What causes this issue?

The system analyzed the data in the document and detected that suspense
accounting cannot or should not be used.
The cause is a type &V1& cause that relates to line item &V2&. The
situation may be one of the following:
Line item "0": The cause does not relate to a specific line item.
Line item is greater than "0": The system detected the cause when it
analyzed the line item in question, and cancelled processing.
The following causes can result in the system being unable to use
suspense accounting:
<ZH>Type T:</> The document contains a tax data table that is not empty.
<ZH>Type M:</> The system is to calculate tax for the document, or take
tax into account. For this reason, you have set a VAT indicator.
<ZH>Type O:</> The system posts items to an open item account.
<ZH>Type X: </>The system posts to a G/L account of open item management
and document splitting is activated in the general ledger (attribute
XOPVW not empty or attribute XLGCLR not empty).
<ZH>Type D:</> The system posts items to a customer or vendor account.
<ZH>Type B:</> The Business Add-In that is called does not permit
suspense accounting.
<ZH>Type E:</> The check module detected a problem.

System Response

This is generally not an error.
The automatic error correction function has modified the data of the
original document. However, the system does not attempt to use suspense
accounting for values derived in this way.

How to fix this error?

Call the <DS:TRAN.ACC_ECS_MAINTAIN>Edit ECS Items</> transaction and
process the document.

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.