A possible fix for the issue could be as below:
- In MATLAB run the command "prefdir" and copy the path.
- It should look like - C:\Users\USERNAME\AppData\Roaming\MathWorks\MATLAB\R2018a
- Terminate all MATLAB instances
- Navigate to the folder and remove or rename the directory HtmlPanel
- Restart MATLAB
If that does not work, clearing the temp folder and restarting MATLAB also may help.
- Open in Explorer: C:\Users\<UserName>\AppData\Local\Temp
- Delete the data inside this Folder.
- Restart MATLAB and try to open LiveEditor.
Thanks.