SAP Note 18420 - Taking over old asset data - accumulated values cannot be en

Symptom:

You cannot enter accumlated values when taking over old asset data.
Key words: AS91 AS94 Taking over old data

Cause and prerequisites

You have flagged the asset class as a class for line-item settlement.

Solution
In asset classes for line-item settlement, you must enter accumulated values as transactions in the transaction screen. Press the pushbutton "Transactions" to do this".
If you do not require this, you must change the asset class or use a different one.