Cannot open two IntelliJ IDEs simultaneously due to shared directory path conflict

Problem

When IntelliJ IDEA is opened, if double-click Rider's icon to open it, the Rider UI cannot be pulled up, only IntelliJ IDEA's UI can be displayed.

Cause

IDE Directories are set to same directory in both IntelliJ IDEA and Rider.

Troubleshooting Steps

Capture logs for both IntelliJ IDEA and Rider via Help | Collect Logs and Diagnostic Data. Check idea.log in both of them, search "IDE Started", and scroll down slowly to locate the log below:

2024-06-25 12:04:11,552 [     62]   INFO - #c.i.p.i.b.AppStarter - locale=en_US JNU=UTF-8 file.encoding=UTF-8
    idea.config.path=/Users/username/Library/Application Support/JetBrains/Rider2024.1
    idea.system.path=/Users/username/Library/Caches/JetBrains/Rider2024.1
    idea.plugins.path=/Users/username/Library/Application Support/JetBrains/Rider2024.1/plugins -> java.nio.file.NoSuchFileException: /Users/jeromeguan/Library/Application Support/JetBrains/Rider2024.1/plugins
    idea.log.path=/Users/username/Library/Logs/JetBrains/Rider2024.1

Make sure those directories (idea.config.path, idea.system.path, idea.plugins.path, idea.log.path) are different in IntelliJ and Rider.

Solution

If these directories are same, please specify different path for your IntelliJ IDEs. https://www.jetbrains.com/help/idea/directories-used-by-the-ide-to-store-settings-caches-plugins-and-logs.html#change-ide-dirs