I've just tested with Stockcar 90 and the included FA liveries - worked.
Order was:
- Make Livery modifications using the Custom Livery Tool.
- Activate Custom Livery Tool via JSGME.
- Run Custom Grid Tool. Click Activate, leave running.
Attachment 228517
Double check that the Aston GT3 directory doesn't have any files with funny characters, trailing spaces, or any additional material like -copy files or .jpgs or something. I had to tighten up control on the file naming in the last version, but I clearly didn't do a good enough job handling unexpected inputs. Will be making this more robust in the future.