I recently connected by TP-Link Kasa account to Smartthings and have successfully connected all of my smart outlets, but none of the smart switches are showing up. It shows that Smartthings is able to connect to bulbs, outlets, and switches, but only my outlets are showing up. Switch is HS200
You may want to contact ST support at https://support.smartthings.com
In this case i think you would contact TP-link support. Those devices are only considered “compatible with SmartThings”, so the manufacturer manages the integration.