Widget Creation Failure

I have an update site that installs fine into XPD 6.2/6.2.1, but when I use the Notes 8.5.1 “Configure a widget from…Features and Plugins on an Update Site” wizard, it does not complete. I specify my local site.xml, click Load, and I see the 5 features contained in my update site. I select them all and continue with the wizard. My plugins are not signed, so I get the “Install this plug-in” choice, but for only some of the plugins I expected. Then I get a message box titled Widget Creation Failure with the following text: The widget failed to be created. Check the log for errors. I do not see anything in the log at this point. Then right on top of that I get the message “Update is complete. You must restart for the updates to take effect. Do you want to restart now?” When I restart I see the provisioning message and the few plug-ins that did get installed end up being removed and I am back to square one.

Can anyone tell me how I can find out why the widget creation failed?

Subject: Required plug-in was missing

If a required plug-in is missing, this is what happens. Not very graceful or informative.