Message type: E = Error
Message class:  ATO_CUSTOMER - ATO Messages for the End User 
Message number: 121
Message text: Item check failed. Please check log.
Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of messages in the SAP system have a message text, however this is frequently insufficient to comprehend or resolve the problem.
To make things easier, more detailed information is frequently added to describe the issue, how to fix it, and the necessary steps or configuration modifications.
Unfortunately, there isn't any extra information in this error notice.
First, use our AnswerBot below to get a possible cause and solution (requires a premium subscription).
Also, review the in-depth Common Questions & Answers listed below; you could discover a solution there or be able to connect with others who have faced similar challenges.
You can also try searching the SAP support portal (support.sap.com) but you need a special user ID to access it. It is possible that an SAP support note exists that provides additional details about the mistake or even steps for fixing it.
The SAP error message ATO_CUSTOMER121, which states "Item check failed. Please check log," typically occurs in the context of Advanced Variant Configuration (AVC) or when dealing with configurable materials in SAP. This error indicates that there is an issue with the configuration of a specific item in a sales order or a similar document. Causes:
Configuration Issues: The item being configured may not meet the required constraints or dependencies defined in the configuration profile. Missing Characteristics: Required characteristics for the configuration might be missing or not properly assigned. Inconsistent Data: There may be inconsistencies in the master data related to the configurable material, such as incorrect settings in the material master or class. Validation Errors: Custom validation rules or checks defined in the configuration may be failing. Logistics Settings: Issues with the logistics settings or the way the item is set up in the system can also lead to this error. Solutions: Check the Configuration Log: The first
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
ATO_CUSTOMER120 All changes of version &1 are included in versions &2 to &3.
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
ATO_CUSTOMER119 Version &1 was set to outdated while versions &2 to &3 were imported.
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
ATO_CUSTOMER122 Check for &2 items of type &1 started
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
ATO_CUSTOMER123 Packages have different transport layers.
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
Click on this link to search all SAP messages.