Okay, I’ve tested the extension on both Windows 11 and Mac OS Sequoia using the latest stable version of Aseprite, which at the moment is 1.3.10.1. It’s possible that since v1.3.11 is still in beta (not sure if you’re on -beta1 or -beta2) that not all of the API features have been implemented/are working correctly. For the time being I’d recommend rolling back to the stable version of Aseprite.