Configure button won't show on custom widget

It's a subtle issue, but I noticed you tagged this as 9.0. If this is for 9, then the assembly for custom control type and property type rules should identify Telligent.Evolution.Controls or Telligent.Evolution.Api instead of Telligent.Evolution.Platform. These were unified to the new Platform assembly in 10.x.

<propertyGroup id="options" resourceName="Options">
	<property id="fragmentHeader" resourceName="CF_Title" dataType="string" defaultValue="${resource:Leaderboard_Name}" controlType="Telligent.Evolution.Controls.ContentFragmentTokenStringControl, Telligent.Evolution.Controls" />
	<property id="viewType" resourceName="View" dataType="string" defaultValue="full">
		<propertyValue value="full" resourceName="View_Default" />
		<propertyValue value="simple" resourceName="View_Simple" />
	</property>
	<property id="pageSize" resourceName="PageSize" dataType="int" defaultValue="10">
		<propertyRule type="Telligent.Evolution.Controls.PropertyRules.MinMaxValueRule, Telligent.Evolution.Controls" minValue="1" maxValue="100" />
	</property>
	<property id="showValue" resourceName="ShowValueColumn" dataType="bool" defaultValue="true" />
	<property id="showCurrentUser" resourceName="ShowCurrentUserPosition" dataType="bool" defaultValue="true" />
    <property id="selectedLeaderboard" resourceName="SelectedLeaderboard" dataType="custom" controlType="Telligent.Evolution.Controls.LeaderboardLookupPropertyControl, Telligent.Evolution.Api" width="95%" />
</propertyGroup>

That would make sense if there wasn't already another custom widget using this very Configuration. On that widget the configure button appears, on it's clone, it doesn't. How could it not appear if to widgets have the exact same code but a different id?

The widget where the button is appearing is also referencing Telligent.Evolution.Platform and it's running on 9.x? And in that case, if you click on the rendered configure button, it successfully renders the configuration form modal? That shouldn't work.

yes, it's also referencing Telligent.Evolution.Platform and it's running on version 9.1 and yes, it successfully renders the configuration from the modal. 

That's strange... That said, I can reproduce the issue you saw in 9 with the original configuration, and adjusting its references corrects it.