LM Studio is an open source app for macOS/Windows/Linux for running LLMs on your own computer. It's great for troubleshooting.
PlanExe processes more text than regular chat. You will need expensive hardware to run a LLM at a reasonable speed.
In the llm_config.json find a config that starts with lmstudio- such as "lmstudio-qwen2.5-7b-instruct-1m".
Inside LM Studio, find the model with that exact id and download it. Here is the qwen model on huggingface. It's around 4.5 GB to download.
Inside LM Studio, go to the Developer page (CMD+2 or Windows+2 or Ctrl+2). Start the server.
The UI should show Status: Running [x] and Reachable at: http://127.0.0.1:1234.
Inside PlanExe, when clicking Submit, a new Output Dir should be created containing a log.txt. Open that file and scroll to the bottom, see if there are any error messages about what is wrong.
Report your issue on Discord. Please include info about your system, such as: "I'm on macOS with M1 Max with 64 GB.".