Hi Martin,
If you have the latest FEFLOW 8.1 version, I would strongly recommend not to use
the old plugin. The functionality of connecting the wells and define pairs
injection-production via an open-loop system are now available directly in the
FEFLOW GUI. The functionalities are accessible through the geothermal extension
of the Well Manager.
You can take a look on this short demo
video: https://www.youtube.com/watch?v=3l1BLLYeRRs
Feel free to reach out FEFLOW support to walk you through the new features.
Best regards
Carlos