Hello,
Indeed, the filtering will not work if you enable the server-side pagination only. The reason is that the server filtering should be enabled in combination with the pagination, in order to be able to search in pages, that are not loaded in the Grid. Please enable the mentioned serverFiltering as demonstrated in the example below:
https://dojo.telerik.com/@nenchef/uJEwiCoZ
Hope this information helps.
Regards,
Nencho
Progress Telerik