Thank you for contacting us. You should be able to load again this plugin from the Office store and solve the problem.
To do so, in Microsoft Word,
1. Remove the plugin that has error: choose Insert then MyAdd-ins, select the plugin then the Remove option
2. Add MyScript Math Sample from the Office Store: choose Insert then Store, then search MyScript Math Sample and tap Add
3. Choose Home then Show Taskpane to use MyScript Math sample
The support team