Ensure your version of Adobe Illustrator supports legacy CEP extensions. If you are using newer versions, you may need to enable "PlayerDebugMode" in your system registry/plist to allow unsigned extensions. Grids Won't Glue Together
The Ultimate Guide to Mesh Tormentor For Adobe Illustrator 0.44.2 Mesh Tormentor For Adobe Illustrator 0.44.2
I can confirm if the 0.44.2 version is stable for your setup or suggest alternatives. Illustrator Mesh Tormentor - Adobe Community Ensure your version of Adobe Illustrator supports legacy