Message type: E = Error
Message class:  HRPIQ000RULES - Messages for CM Rules 
Message number: 004
Message text: Message class &1 does not exist
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 HRPIQ000RULES004 indicates that a specific message class (in this case, &1) does not exist in the system. This error typically arises in the context of SAP HR (Human Resources) or SAP Student Lifecycle Management (SLCM) modules, where message classes are used to manage and display messages to users.
Cause: Missing Message Class: The specified message class has not been created or is not available in the system. Incorrect Configuration: There may be a configuration issue where the system is trying to reference a message class that is not defined. Transport Issues: If the message class was supposed to be transported from another system (like Development to Production), it may not have been included in the transport request.
Solution: Check Message Class: Go to transaction code SE91 (Message Class Maintenance) in SAP. Enter the message class name that is causing the error (replace &1 with the actual name). If the message class does not exist, you
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
HRPIQ000RULES003 Message &1 is not available in message class &2
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
HRPIQ000RULES002 BAdI filter value &1 is not defined
What causes this issue?  Filter value &V1& of the <DS:GLOS.5C733369F735D311AE620060B03C9BBE>business add-in</> is not defined in v...
HRPIQ000RULES005 Enter a message number
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
HRPIQ000RULES006 Enter a user
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.