Slitherine

just started to play this. On first play played a bit then finished for the night liked it. However following day tried to play and launcher comes up then press play and nothing happens as says is already open. On checking in my steam it indeed says still running although should already have closed when i closed it from previous day (i dont leave my PC on overnight ever) . Now i noticed that it says irt is running in my library. Have tried many ways of closing it but no joy (gone into task manager and program or any process from Slitherine shows as running. How can i get this fixed? (only way to stopping it is to completely shut down steam. Never had this issue on any of my 2000 steam games before.