MySMS is a free Yeastar software used for TG gateway. It's still available to use, but we don't offer bug fix and update anymore. However, you will have the Flash Player issue when you try to send SMS.
As Adobe announced, the Flash Player has been end of life. See link: https://www.adobe.com/products/flashplayer/end-of-life.html
Also, Google has removed the Flash Player on their Chrome browser and does not support it anymore. See link: https://support.google.com/chrome/answer/6258784/flash-player-is-no-longer-available?hl=en
Downgrade Chrome to an old version. Any version before 88 is fine, like
- Google Chrome: version 87
How to downgrade to use Flash Player: https://www.youtube.com/watch?v=MRfAtSAlXYk