This issue is not with OSMC but with the add-on your running. I did a quick web search and was able to find that the person who wrote it stopped maintaining it quite a while back and it would seem recent changes required an update to the add-on for it to keep working. You can find more information about this on the Kodi forum…
https://forum.kodi.tv/showthread.php?tid=205551&pid=2892822#pid2892822