All product from KC Softwares are discontinued.
The developer answered their own question on this forum.
https://www.wilderssecurity.com/threads/sumo-keep-your-software-up-to-date.314623/page-196
https://www.ghacks.net/2023/09/11/kc-softwares-maker-of-sumo-and-other-apps-is-shutting-down/
Most similar product is ucheck
https://www.adlice.com/ucheck/