When you go to the userlib folder in your project folder, you will see files with the name “apmagent_obfuscated_merged_<version>.jar”. There you can delete the apmagent_obfuscated_merged_<older version>.jar file.
When upgrading a module that has .jar files, the Mendix platform/ modeler (studio pro) is never deleting older .jar files. That's why it's in the installation manual.
How would you like to see that the installation manual is improved?
Hope this helps.
Jeffrey, How do I mark the answer as accepted?
Problem solved. Probably deleted a jar file that was needed.
Both App Store modules have been reinstalled. Had some difficulty because language translation has disappeared. But finally succeeded.
The instructions in the installation manual are not really useful:
To upgrade an APM 2 agent follow these steps
1. In Mendix Studio Pro with your app import to replace the Mendix Application Performance
Monitor module from the Mendix App Store.
2. Remove the old APM 2 agent jar from your userlib folder
3. Before testing in Mendix Studio Pro, use the Clean deployment directory option.
What are the ‘old APM agent jar’ files?