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I fixed it!
It seems the program remembers the resolution it was opened in. There was once a glitch with the resolution.
After the glitch, it opened in a 1px window.
In the shortcut properties, I set the "Window" value to "Maximize".
The program opened and started working.
After opening it in full-screen mode, I changed the resolution, exited, set "Normal window size" in the properties, and the program started working as before, without any problems.