Hi derkork,
I've just installed IntelliJ IDEA 14 and 15, and Plastic SCM for Mac on a clean Mac using El Capitan. I've copied the zipped contents Manu posted above into /Applications/IntelliJ\ IDEA\ <version>.app/Contents/plugins, as I think you already did. I also confirmed that the cm executable was in the command line. I configured macplastic using the macplastic.app application. Surprisingly, I didn't find any trouble using Plastic inside IDEA. I was able to create a new project from VCS checkout or creating a new workspace for a new IDEA project. Checkin, checkout, update and all other functionalities didn't cause any trouble and only one cm shell process was running at the same time.
At this point, can you verify that the directory /Users/j.thomae/Library/Caches/IntelliJIdea15/tmp exists and your user has write permissions in it? If it didn't, it might be possible that IDEA can't find the commfile passed to the cm shell process. This would mean that IDEA can't assure that the cm shell is ready to accept commands, opening new shells as retries.
I would ask you to reinstall MacPlastic, backing up your config files. They shouldn't be inside the application directory but in your home directory, as you said. That is the default behaviour (as I've just tested and confirmed) and your /Applications/macplastic.app/Contents/MonoBundle directory should only contain remoting.conf and macplastic.log.conf, which aren't user-specific. I'd ask you to configure MacPlastic using the GUI, either opening it for the first time when no configuration is present in your system or through the preferences dialog. You can also manually launch the client configuration window by executing:
open /Applications/macplastic.app --args --configure
As Manu said, the "Configure client" is not compatible with MacPlastic at the moment. How did you configure plastic the first time?
If reinstalling MacPlastic doesn't work and you still experience issues, I'd like you to configure the cm logging. You'll have to write this content inside the file /Application/macplastic.app/Contents/MonoBundle/cm.log.conf (you'll probably have to create it):
<log4net>
<appender name="RollingFileAppender"
type="log4net.Appender.RollingFileAppender">
<file value="${HOME}/.plastic4/cm.log.txt" />
<appendToFile value="true" />
<rollingStyle value="Size" />
<maxSizeRollBackups value="10" />
<maximumFileSize value="100MB" />
<staticLogFileName value="true" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%date %property{TransactionID} %username at %property{ClientMachine} %-5level %logger - %message%newline" />
</layout>
</appender>
<root>
<level value="DEBUG" />
<appender-ref ref="RollingFileAppender" />
</root>
</log4net>
Also, set your macplastic root log level value to DEBUG by editing /Applications/macplastic.app/Contents/MonoBundle/macplastic.log.conf like this:
<log4net>
<!-- appender definitions -->
<root>
<level value="DEBUG" />
<appender-ref ref="RollingFileAppender" />
</root>
</log4net>
After the failed execution you'll find a cm.log.txt file inside ${HOME}/.plastic4. We'd appreciate if you could sent it to us along with ${HOME}/.plastic4/macplastic.log.txt and the IDEA log (it can be found by clicking on the "Help->Show Log in Finder" IDEA menu option).
Regards,
Miguel