Xiaomi mi desktop 1s does not go to sleep, how to force?

Question

Monitors

OS - KDE - I decided to update the monitors, I took Xiaomi mi desktop 1s - after connecting, a problem was discovered - they do not want to go to sleep. I.e. Before that, sleep after inactivity was set up, and everything worked with old monitors. Now the monitor goes out on a timer, and wakes up again after about 10 seconds. And so in a circle. Fading, waking up, fading, waking up. I did not change the settings, I only changed the monitors. How can the problem be solved?