The page is syncing a live Google sheet without caching (because I want people to get the latest quantity).

Based on a previous support ticket, I have set a conditional formatting rule on the Quantity Remaining column, 

if cell value = 0 then set Row CSS class to already-claimed 

I then added a custom CSS rule to the table.

.already-claimed {
    text-decoration: line-through;
    background-color: #CCCCCC;
    color: #444444;
}

However, the background color is only working on odd rows (which also look like they're slightly orange, but that could be an optical illusion). Fortunately the important thing is that the text-decoration is working. But it would be really nice if we could get the background color to work as well.

It looks like your td rule is overriding my custom rule, and it has !important but I can't add !important to my custom rule.

.wpdt-c.wpDataTablesWrapper table.wpdtSimpleTable tr.odd td, .wpdt-c .wpDataTablesWrapper table.wpDataTable tr.odd td {
  background-color: #F2A5182E !important;
}

So it only happens to work because the odd row rule has alpha value. I worked round it by adding an alpha value to the white of the even row, but it's a little confusing.

Thank you! FWIW I didn't realize that the main settings would override, I figured it would be the other way around and that main settings were just a default. But now that I know I got it to work! Thank you!