Unable to click on checkbox in selenium

I have tried xPath,CssSelector,tagName,Name,id but it always throw an error that "element not visible"

HtLM is

<div class="alertType nonEv" style="display: block;">
<span style="font-family:designk-bold; font-size:x-large; color:#444">MAINTENANCE & DIAGNOSTICS ALERTS</span>
<br>
<ul>
<li>
<span>500 miles before maintenance</span>
<input id="" class="checkbox" type="checkbox" value="Y" name="">
<label class="noShow"></label>
<input id="" class="checkbox" type="checkbox" value="Y" name="">
<label class="noShow"></label>
<input id="maint100" class="checkbox" type="checkbox" value="Y" name="maint100">
<label class="col3" for="maint100"></label>
</li>

Please help