Thanks for contacting Syncfusion support.
We are unable to reproduce the reported issue. To perform multi-sorting, hold CTRL key and press LEFT mouse button and to clear sorting for a particular column use SHIFT + LEFT mouse button.
Also please provide us the below information regarding your problem.
1. Essential studio version used.
2. View page or Grid rendering code.
3. Screenshot of Network tab to check request send while sorting.
4. Screenshot of browser console to check any script error if any.
Please refer to the below link for more information regarding Multi-Sorting feature.
Please let us know if you have any queries.
Regards,
Madhu Sudhanan P