Hello!
First, do you have aseprite extension installed? If not, you can open addon settings in blender, press “Install Aseprite Extension”, and drag the extension file into aseprite window. And in case it is installed, make sure it is not disabled in “Edit > Preferences > Extensions”.
Otherwise i’m kinda out of guesses (is it demo or a custom build with scripting disabled?) But you could try to launch it independently and connect to it:
- In Aseprite press File > Sync.
- In Blender press “Connect” on the addon panel.