You try to process an image with GraXpert from PixInsight but you get an error message related to AI model, file doesn't exist.

This is a known issue in GraXpert.

To fix that, you have to:

1. Manually remove old AI models (see locations below),
2. Run GraXpert application and process an image (background extraction and denoising) to force AI model download.

My Quick User Guide gives location of AI models but in short:

• Windows: C:\Users\AppData\Local\GraXpert\GraXpert\ai-models\
• macOS: /Users//Library/Application Support/GraXpert/ai-models/
• Linux: /home//.local/share/GraXpert/ai-models/

If there is no AI model installed, the process will launch GraXpert which will download last version. This takes time and if you stop the process during download, you'll have to remove manually unterminated downloaded file(s). Currently GraXpert do not give information to PixInsight about download progress. So, it's better to launch the AI model download from GraXpert application. Indeed, from Application you know exactly when AI model is downloading and when image is processed.