How To Fix WB015 - Version no. &1 for customer &2 and assortment list &3 is already blocked

SAP Error Message - Details

• Message type: E = Error

• Message class: WB - Messages for assortment list

• Message number: 015

• Message text: Version no. &1 for customer &2 and assortment list &3 is already blocked

What causes this issue?

The version of the assortment list is to be blocked for processing.
However, the version is already blocked by another process.

System Response

Processing of the assortment list is not possible.

How to fix this error?

Do not start any parallel proceses for the same assortment list.

Error message extract from SAP system. Copyright SAP SE.