似乎我在给它分配了错误的元素并查看了调试器：

It seems that i was assigning it the wrong element and looking at debugger:

<td width="230"><input type="checkbox" name="extend" value="on" onchange="javascript:disabledPagination();" id="orgextend">

然后使用ID和.Checked = $ true解决了我的问题：

Then using the ID and .Checked = $true has solved my issue:

$chk = $ie.Document.getElementById("orgextend").Checked = $true