It seems that
1) your user control is not recreated after the postback, which is a requirement in ASP, otherwise its instance will be lost and thus no events will be fired. This demo
shows an example logic of recreating user controls and this article
explains the case in more detail.
2) you may want to initiate partial postbacks inside the RadWindow and this article
explains how to do this. I also advise that you make sure the RadWindow whose ContentTemplate is used for this is kept outside of a RadWindowManager.
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