Message type: E = Error
Message class:  HRPIQ00MBSS2 - Messages for Course Registration UI (Used only for Frontend) 
Message number: 004
Message text: You have already registered module &1
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 HRPIQ00MBSS2004, which states "You have already registered module &1," typically occurs in the context of the SAP HR (Human Resources) module, particularly when dealing with the registration of training modules or courses in the system.
Cause: This error usually arises when a user attempts to register for a training module or course that they have already registered for. The system checks the registration records and finds that the user is already associated with the specified module (indicated by &1).
Solution: To resolve this error, you can take the following steps: Check Existing Registrations: Review the current registrations for the user in the system. You can do this by navigating to the relevant transaction (e.g., using transaction codes like HRPIQ00 or S_AHR_61016300 depending on your system configuration) to see if the user is already registered for the module. Unregister if Necessary: If the user needs to change their registration, you may need to
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
HRPIQ00MBSS2003 Module(s) successfully removed from Registration Cart
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
HRPIQ00MBSS2002 Module(s) successfully added to Registration Cart
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
HRPIQ00MBSS2005 You are already on the waitlist of module &1
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
HRPIQ00MBSS2006 Module &1 is already in your Registration Cart
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.