Control on a custom ribbon doesn't work

[Magster]

Hi all - can anyone tell me why the following code doesn't work? When I open the form that this ribbon code is used in, the Ascending and Descending buttons appear, but they are not available to use. The other two buttons work just fine. Thanks in advance for any suggestions.

<customUI xmlns="http://schemas.microsoft.com/office/2006/01/customui" >
<ribbon startFromScratch="true">
<tabs>
<tab id="Close" label="Navigation">
<group id="grpExit2" label="Close">
<button id="cmdCloseForm2" label="Close Form" imageMso="FileCloseDatabase" size="large" onAction="onCloseObject"/>
</group>
<group id="grpCustomGroup" label="my custom group">
<control idMso="AdpOutputOperationsSortAscending" label="Sort Descending" enabled="true"/>
<control idMso="AdpOutputOperationsSortDescending" label="Sort Ascending" enabled="true"/>
<control idMso="FilterBySelection" label="Filter by Selection" enabled="true"/>
<control idMso="FilterToggleFilter" label="Toggle Filter" enabled="true"/>
</group>
</tab>
</tabs>
</ribbon>
</customUI>