RI Nexus Shopify solution not working...

[TrendyMcKenzie]

I live in RI and we only charge taxes on clothing when the amount reaches over $250.  I followed the Shopify Nexus directions for RI, I created a manual collection titled tax:clothing and added all clothing to the collection. It said that that was all I had to do, however, it’s not collecting taxes on clothing purchases over $250.  I’m not sure what else I’m supposed to do! Help!