If you've added an indicator to a thinkorswim chart and it's not appearing, it may be that you have too many indicators on the chart.
Thinkorswim will automatically prevent the showing of indicators if there isn't enough room to show all the indicators added to a chart. So you may see that an indicator is showing up in the list of indicators added to a chart, but you can't see it on the chart.
To confirm that your indicator is installed and working properly, try opening a new chart (you can Detach a chart to make a copy of it), and then add only that one indicator. If there's room for it to appear, it should now be visible.
Another approach is to change the order of your indicators so that the desired indicator appears higher-up in the list, so it's not the one that's hidden. You can change the order of indicators using the up and down arrow icons in Edit Studies.
If this doesn't resolve the issue, it may be that another indicator is overwriting your indicator. This could happen if there are two indicators trying to paint the bar colors. This will often generate an error condition, which can be viewed by clicking the white "i" inside a circle at the upper-left corner of the chart. That will report what the error condition is. If this is the case, then try removing the other indicator that's hiding your indicator's functionality.
If none of these solutions work, you can contact Thinkorswim support for further assistance.