Message type: E = Error
Message class:  LSO_CORRESPONDENCE - Correspondence Messages 
Message number: 421
Message text: Course &1 is not a curriculum
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 LSO_CORRESPONDENCE421 indicates that the course you are trying to reference is not recognized as a curriculum in the Learning Solution (LSO) module of SAP. This error typically arises when there is an attempt to link a course to a curriculum, but the system does not recognize the course as part of a valid curriculum structure.
Cause: Course Not Defined as Curriculum: The course you are trying to use is not defined as a curriculum in the system. Incorrect Course ID: The course ID you are using may be incorrect or does not exist in the system.
Configuration Issues: There may be configuration issues in the Learning Solution module that prevent the course from being recognized as part of a curriculum. Data Inconsistencies: There could be inconsistencies in the data related to the course or curriculum.
Solution: Check Course Definition: Verify that the course is correctly defined in the system. Ensure that it is
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
LSO_CORRESPONDENCE420 No delivery method is stored for course &1
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
LSO_CORRESPONDENCE419 Course &1 has no time schedule
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
LSO_CORRESPONDENCE422 Cannot generate instance of read class for text variables
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
LSO_CORRESPONDENCE500 *************************************************************************
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.