My apologies for not updating this thread! We released the update to the Album Art Tile which brings support for the cast-web-api devices to everyone in an early January release. It was included in the following update:
It sounds like that’s where the problem lies. The cast web device in SmartThings needs to be updating in order for SharpTools to update. 
Can you clarify what is working? It sounds like the cast-web-api integration was able to discover your devices and you can use those devices to send announcements… but you’re not seeing the device details update with track related information?
Have you posted in the cast-web-api thread in the SmartThings community?