Message type: E = Error
Message class:  MSI_CUST_PRODCAT - Message Class for Loading to Category Hierarchies 
Message number: 300
Message text: Material groups: application &1 invalid
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 "MSI_CUST_PRODCAT300 Material groups: application &1 invalid" typically occurs in the context of material master data management, particularly when dealing with material groups in the SAP system. This error indicates that there is an issue with the configuration of material groups in relation to the application area specified.
Cause: Invalid Application Area: The application area specified in the material group configuration does not exist or is not valid. This could happen if the application area has been deleted or if there is a typo in the configuration. Missing Configuration: The material group may not be properly configured in the system, leading to inconsistencies. Data Inconsistency: There may be inconsistencies in the data related to the material groups, such as missing entries in the relevant tables.
Solution: Check Material Group Configuration: Go to the configuration settings for material groups in the SAP system (Transaction code: SPRO). Navigate to the relevant section for material group configuration and
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
MSI_CUST_PRODCAT205 Key mapping for service type &1 exists, but category &2 not found
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
MSI_CUST_PRODCAT204 Service types: error retrieving data
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
MSI_CUST_PRODCAT301 Material groups: no data exists
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
MSI_CUST_PRODCAT302 Material groups: root category not found
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.