I had this problem where when I plugged-out or in my Charging cable, my refresh rate always reset to 40hz, I always had to open the intel panel and put it back on to 60hz again 😞
If do you know how to fix it please respond to my messages, and if you do you're an angel.
To be able to further assist you, I request some additional details, such as:
In the meantime, you can try reinstalling the display driver, which is done as follows:
Hope this helps, I await your reply